New upstream version 2.10.0~RC1

app/operations/layer-modes/Makefile.am

@@ -0,0 +1,79 @@
+## Process this file with automake to produce Makefile.in
+
+AM_CPPFLAGS = \
+	-DG_LOG_DOMAIN=\"Gimp-Layer-Modes\"	\
+	-I$(top_builddir)			\
+	-I$(top_srcdir)				\
+	-I$(top_builddir)/app			\
+	-I$(top_srcdir)/app			\
+	$(CAIRO_CFLAGS)				\
+	$(GEGL_CFLAGS)				\
+	$(GDK_PIXBUF_CFLAGS)			\
+	-I$(includedir)
+
+noinst_LIBRARIES = \
+	libapplayermodes-generic.a	\
+	libapplayermodes-sse2.a		\
+	libapplayermodes-sse4.a		\
+	libapplayermodes.a
+
+libapplayermodes_generic_a_sources = \
+	gimp-layer-modes.c			\
+	gimp-layer-modes.h			\
+	\
+	gimpoperationlayermode.c		\
+	gimpoperationlayermode.h		\
+	gimpoperationlayermode-blend.c		\
+	gimpoperationlayermode-blend.h		\
+	gimpoperationlayermode-composite.c	\
+	gimpoperationlayermode-composite.h	\
+	\
+	gimpoperationantierase.c		\
+	gimpoperationantierase.h		\
+	gimpoperationbehind.c			\
+	gimpoperationbehind.h			\
+	gimpoperationdissolve.c			\
+	gimpoperationdissolve.h			\
+	gimpoperationerase.c			\
+	gimpoperationerase.h			\
+	gimpoperationmerge.c			\
+	gimpoperationmerge.h			\
+	gimpoperationnormal.c			\
+	gimpoperationnormal.h			\
+	gimpoperationpassthrough.c		\
+	gimpoperationpassthrough.h		\
+	gimpoperationreplace.c			\
+	gimpoperationreplace.h			\
+	gimpoperationsplit.c			\
+	gimpoperationsplit.h
+
+libapplayermodes_sse2_a_sources = \
+	gimpoperationlayermode-composite-sse2.c	\
+	\
+	gimpoperationnormal-sse2.c
+
+libapplayermodes_sse4_a_sources = \
+	gimpoperationnormal-sse4.c
+
+
+libapplayermodes_generic_a_SOURCES = $(libapplayermodes_generic_a_sources)
+
+libapplayermodes_sse2_a_SOURCES = $(libapplayermodes_sse2_a_sources)
+
+libapplayermodes_sse2_a_CFLAGS = $(SSE2_EXTRA_CFLAGS)
+
+libapplayermodes_sse4_a_SOURCES = $(libapplayermodes_sse4_a_sources)
+
+libapplayermodes_sse4_a_CFLAGS = $(SSE4_1_EXTRA_CFLAGS)
+
+libapplayermodes_a_SOURCES =
+
+
+libapplayermodes.a: libapplayermodes-generic.a \
+                    libapplayermodes-sse2.a \
+                    libapplayermodes-sse4.a
+	$(AR) $(ARFLAGS) libapplayermodes.a \
+	  $(libapplayermodes_generic_a_OBJECTS) \
+	  $(libapplayermodes_sse2_a_OBJECTS) \
+	  $(libapplayermodes_sse4_a_OBJECTS)
+	$(RANLIB) libapplayermodes.a

app/operations/layer-modes/gimp-layer-modes.h

@@ -0,0 +1,70 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimp-layer-modes.h
+ * Copyright (C) 2017 Michael Natterer <mitch@gimp.org>
+ *                    Øyvind Kolås <pippin@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_LAYER_MODES_H__
+#define __GIMP_LAYER_MODES_H__
+
+
+void                       gimp_layer_modes_init                      (void);
+
+gboolean                   gimp_layer_mode_is_legacy                  (GimpLayerMode           mode);
+
+gboolean                   gimp_layer_mode_is_blend_space_mutable     (GimpLayerMode           mode);
+gboolean                   gimp_layer_mode_is_composite_space_mutable (GimpLayerMode           mode);
+gboolean                   gimp_layer_mode_is_composite_mode_mutable  (GimpLayerMode           mode);
+
+gboolean                   gimp_layer_mode_is_subtractive             (GimpLayerMode           mode);
+
+GimpLayerColorSpace        gimp_layer_mode_get_blend_space            (GimpLayerMode           mode);
+GimpLayerColorSpace        gimp_layer_mode_get_composite_space        (GimpLayerMode           mode);
+GimpLayerCompositeMode     gimp_layer_mode_get_composite_mode         (GimpLayerMode           mode);
+GimpLayerCompositeMode     gimp_layer_mode_get_paint_composite_mode   (GimpLayerMode           mode);
+
+const gchar              * gimp_layer_mode_get_operation              (GimpLayerMode           mode);
+
+GimpLayerModeFunc          gimp_layer_mode_get_function               (GimpLayerMode           mode);
+GimpLayerModeBlendFunc     gimp_layer_mode_get_blend_function         (GimpLayerMode           mode);
+
+GimpLayerModeContext       gimp_layer_mode_get_context                (GimpLayerMode           mode);
+
+GimpLayerMode            * gimp_layer_mode_get_context_array          (GimpLayerMode           mode,
+                                                                       GimpLayerModeContext    context,
+                                                                       gint                   *n_modes);
+
+GimpLayerModeGroup         gimp_layer_mode_get_group                  (GimpLayerMode           mode);
+
+const GimpLayerMode      * gimp_layer_mode_get_group_array            (GimpLayerModeGroup      group,
+                                                                       gint                   *n_modes);
+
+gboolean                   gimp_layer_mode_get_for_group              (GimpLayerMode           old_mode,
+                                                                       GimpLayerModeGroup      new_group,
+                                                                       GimpLayerMode          *new_mode);
+
+const Babl               * gimp_layer_mode_get_format                 (GimpLayerMode           mode,
+                                                                       GimpLayerColorSpace     composite_space,
+                                                                       GimpLayerColorSpace     blend_space,
+                                                                       const Babl             *preferred_format);
+
+GimpLayerCompositeRegion   gimp_layer_mode_get_included_region        (GimpLayerMode           mode,
+                                                                       GimpLayerCompositeMode  composite_mode);
+
+
+#endif /* __GIMP_LAYER_MODES_H__ */

app/operations/layer-modes/gimpoperationantierase.c

@@ -0,0 +1,188 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationantierase.c
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *               2012 Ville Sokk <ville.sokk@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+
+#include "../operations-types.h"
+
+#include "gimpoperationantierase.h"
+
+
+
+static gboolean                   gimp_operation_anti_erase_process             (GeglOperation          *op,
+                                                                                 void                   *in,
+                                                                                 void                   *layer,
+                                                                                 void                   *mask,
+                                                                                 void                   *out,
+                                                                                 glong                   samples,
+                                                                                 const GeglRectangle    *roi,
+                                                                                 gint                    level);
+static GimpLayerCompositeRegion   gimp_operation_anti_erase_get_affected_region (GimpOperationLayerMode *layer_mode);
+
+
+G_DEFINE_TYPE (GimpOperationAntiErase, gimp_operation_anti_erase,
+               GIMP_TYPE_OPERATION_LAYER_MODE)
+
+
+static void
+gimp_operation_anti_erase_class_init (GimpOperationAntiEraseClass *klass)
+{
+  GeglOperationClass          *operation_class  = GEGL_OPERATION_CLASS (klass);
+  GimpOperationLayerModeClass *layer_mode_class = GIMP_OPERATION_LAYER_MODE_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name",        "gimp:anti-erase",
+                                 "description", "GIMP anti erase mode operation",
+                                 NULL);
+
+  layer_mode_class->process             = gimp_operation_anti_erase_process;
+  layer_mode_class->get_affected_region = gimp_operation_anti_erase_get_affected_region;
+}
+
+static void
+gimp_operation_anti_erase_init (GimpOperationAntiErase *self)
+{
+}
+
+static gboolean
+gimp_operation_anti_erase_process (GeglOperation       *op,
+                                   void                *in_p,
+                                   void                *layer_p,
+                                   void                *mask_p,
+                                   void                *out_p,
+                                   glong                samples,
+                                   const GeglRectangle *roi,
+                                   gint                 level)
+{
+  GimpOperationLayerMode *layer_mode = (gpointer) op;
+  gfloat                 *in         = in_p;
+  gfloat                 *out        = out_p;
+  gfloat                 *layer      = layer_p;
+  gfloat                 *mask       = mask_p;
+  gfloat                  opacity    = layer_mode->opacity;
+  const gboolean          has_mask   = mask != NULL;
+
+  switch (layer_mode->real_composite_mode)
+    {
+    case GIMP_LAYER_COMPOSITE_UNION:
+    case GIMP_LAYER_COMPOSITE_AUTO:
+      while (samples--)
+        {
+          gfloat value = opacity;
+          gint   b;
+
+          if (has_mask)
+            value *= *mask;
+
+          out[ALPHA] = in[ALPHA] + (1.0 - in[ALPHA]) * layer[ALPHA] * value;
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b];
+            }
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+      while (samples--)
+        {
+          gint b;
+
+          out[ALPHA] = in[ALPHA];
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b];
+            }
+
+          in  += 4;
+          out += 4;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+      while (samples--)
+        {
+          gfloat value = opacity;
+          gint   b;
+
+          if (has_mask)
+            value *= *mask;
+
+          out[ALPHA] = layer[ALPHA] * value;
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b];
+            }
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_INTERSECTION:
+      while (samples--)
+        {
+          gfloat value = opacity;
+          gint   b;
+
+          if (has_mask)
+            value *= *mask;
+
+          out[ALPHA] = in[ALPHA] * layer[ALPHA] * value;
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b];
+            }
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+    }
+
+  return TRUE;
+}
+
+static GimpLayerCompositeRegion
+gimp_operation_anti_erase_get_affected_region (GimpOperationLayerMode *layer_mode)
+{
+  return GIMP_LAYER_COMPOSITE_REGION_SOURCE;
+}

app/operations/layer-modes/gimpoperationantierase.h

@@ -0,0 +1,53 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationantierase.h
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_ANTI_ERASE_H__
+#define __GIMP_OPERATION_ANTI_ERASE_H__
+
+
+#include "gimpoperationlayermode.h"
+
+
+#define GIMP_TYPE_OPERATION_ANTI_ERASE            (gimp_operation_anti_erase_get_type ())
+#define GIMP_OPERATION_ANTI_ERASE(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_OPERATION_ANTI_ERASE, GimpOperationAntiErase))
+#define GIMP_OPERATION_ANTI_ERASE_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  GIMP_TYPE_OPERATION_ANTI_ERASE, GimpOperationAntiEraseClass))
+#define GIMP_IS_OPERATION_ANTI_ERASE(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_OPERATION_ANTI_ERASE))
+#define GIMP_IS_OPERATION_ANTI_ERASE_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  GIMP_TYPE_OPERATION_ANTI_ERASE))
+#define GIMP_OPERATION_ANTI_ERASE_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  GIMP_TYPE_OPERATION_ANTI_ERASE, GimpOperationAntiEraseClass))
+
+
+typedef struct _GimpOperationAntiErase      GimpOperationAntiErase;
+typedef struct _GimpOperationAntiEraseClass GimpOperationAntiEraseClass;
+
+struct _GimpOperationAntiErase
+{
+  GimpOperationLayerMode  parent_instance;
+};
+
+struct _GimpOperationAntiEraseClass
+{
+  GimpOperationLayerModeClass  parent_class;
+};
+
+
+GType   gimp_operation_anti_erase_get_type (void) G_GNUC_CONST;
+
+
+#endif /* __GIMP_OPERATION_ANTI_ERASE_H__ */

app/operations/layer-modes/gimpoperationbehind.c

@@ -0,0 +1,236 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationbehind.c
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *               2012 Ville Sokk <ville.sokk@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+
+#include "../operations-types.h"
+
+#include "gimpoperationbehind.h"
+
+
+
+static gboolean   gimp_operation_behind_process (GeglOperation       *op,
+                                                 void                *in,
+                                                 void                *layer,
+                                                 void                *mask,
+                                                 void                *out,
+                                                 glong                samples,
+                                                 const GeglRectangle *roi,
+                                                 gint                 level);
+
+
+G_DEFINE_TYPE (GimpOperationBehind, gimp_operation_behind,
+               GIMP_TYPE_OPERATION_LAYER_MODE)
+
+
+static void
+gimp_operation_behind_class_init (GimpOperationBehindClass *klass)
+{
+  GeglOperationClass          *operation_class  = GEGL_OPERATION_CLASS (klass);
+  GimpOperationLayerModeClass *layer_mode_class = GIMP_OPERATION_LAYER_MODE_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name",        "gimp:behind",
+                                 "description", "GIMP behind mode operation",
+                                 NULL);
+
+  layer_mode_class->process = gimp_operation_behind_process;
+}
+
+static void
+gimp_operation_behind_init (GimpOperationBehind *self)
+{
+}
+
+static gboolean
+gimp_operation_behind_process (GeglOperation       *op,
+                               void                *in_p,
+                               void                *layer_p,
+                               void                *mask_p,
+                               void                *out_p,
+                               glong                samples,
+                               const GeglRectangle *roi,
+                               gint                 level)
+{
+  GimpOperationLayerMode *layer_mode = (gpointer) op;
+  gfloat                 *in         = in_p;
+  gfloat                 *out        = out_p;
+  gfloat                 *layer      = layer_p;
+  gfloat                 *mask       = mask_p;
+  gfloat                  opacity    = layer_mode->opacity;
+  const gboolean          has_mask   = mask != NULL;
+
+  switch (layer_mode->real_composite_mode)
+    {
+    case GIMP_LAYER_COMPOSITE_UNION:
+    case GIMP_LAYER_COMPOSITE_AUTO:
+      while (samples--)
+        {
+          gfloat src1_alpha = in[ALPHA];
+          gfloat src2_alpha = layer[ALPHA] * opacity;
+          gfloat new_alpha;
+          gint   b;
+
+          if (has_mask)
+            src2_alpha *= *mask;
+
+          new_alpha = src2_alpha + (1.0 - src2_alpha) * src1_alpha;
+
+          if (new_alpha)
+            {
+              gfloat ratio = in[ALPHA] / new_alpha;
+              gfloat compl_ratio = 1.0f - ratio;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b] * ratio + layer[b] * compl_ratio;
+                }
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b];
+                }
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+      while (samples--)
+        {
+          gfloat src1_alpha = in[ALPHA];
+          gfloat new_alpha;
+          gint   b;
+
+          new_alpha = src1_alpha;
+
+          if (new_alpha)
+            {
+              for (b = RED; b < ALPHA; b++)
+                out[b] = in[b];
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                out[b] = layer[b];
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+      while (samples--)
+        {
+          gfloat src1_alpha = in[ALPHA];
+          gfloat src2_alpha = layer[ALPHA] * opacity;
+          gfloat new_alpha;
+          gint   b;
+
+          if (has_mask)
+            src2_alpha *= *mask;
+
+          new_alpha = src2_alpha;
+
+          if (new_alpha)
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b] + (in[b] - layer[b]) * src1_alpha;
+                }
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b];
+                }
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+      case GIMP_LAYER_COMPOSITE_INTERSECTION:
+      while (samples--)
+        {
+          gfloat src1_alpha = in[ALPHA];
+          gfloat src2_alpha = layer[ALPHA] * opacity;
+          gfloat new_alpha;
+          gint   b;
+
+          if (has_mask)
+            src2_alpha *= *mask;
+
+          new_alpha = src1_alpha * src2_alpha;
+
+          if (new_alpha)
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b];
+                }
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+    }
+
+  return TRUE;
+}

app/operations/layer-modes/gimpoperationbehind.h

@@ -0,0 +1,53 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationbehind.h
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_BEHIND_H__
+#define __GIMP_OPERATION_BEHIND_H__
+
+
+#include "gimpoperationlayermode.h"
+
+
+#define GIMP_TYPE_OPERATION_BEHIND            (gimp_operation_behind_get_type ())
+#define GIMP_OPERATION_BEHIND(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_OPERATION_BEHIND, GimpOperationBehind))
+#define GIMP_OPERATION_BEHIND_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  GIMP_TYPE_OPERATION_BEHIND, GimpOperationBehindClass))
+#define GIMP_IS_OPERATION_BEHIND(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_OPERATION_BEHIND))
+#define GIMP_IS_OPERATION_BEHIND_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  GIMP_TYPE_OPERATION_BEHIND))
+#define GIMP_OPERATION_BEHIND_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  GIMP_TYPE_OPERATION_BEHIND, GimpOperationBehindClass))
+
+
+typedef struct _GimpOperationBehind      GimpOperationBehind;
+typedef struct _GimpOperationBehindClass GimpOperationBehindClass;
+
+struct _GimpOperationBehind
+{
+  GimpOperationLayerMode  parent_instance;
+};
+
+struct _GimpOperationBehindClass
+{
+  GimpOperationLayerModeClass  parent_class;
+};
+
+
+GType    gimp_operation_behind_get_type (void) G_GNUC_CONST;
+
+
+#endif /* __GIMP_OPERATION_BEHIND_H__ */

app/operations/layer-modes/gimpoperationdissolve.c

@@ -0,0 +1,168 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationdissolve.c
+ * Copyright (C) 2012 Ville Sokk <ville.sokk@gmail.com>
+ *               2012 Øyvind Kolås <pippin@gimp.org>
+ *               2003 Helvetix Victorinox
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+
+#include "../operations-types.h"
+
+#include "gimpoperationdissolve.h"
+
+
+#define RANDOM_TABLE_SIZE 4096
+
+
+static gboolean                   gimp_operation_dissolve_process             (GeglOperation          *op,
+                                                                               void                   *in,
+                                                                               void                   *layer,
+                                                                               void                   *mask,
+                                                                               void                   *out,
+                                                                               glong                   samples,
+                                                                               const GeglRectangle    *result,
+                                                                               gint                    level);
+static GimpLayerCompositeRegion   gimp_operation_dissolve_get_affected_region (GimpOperationLayerMode *layer_mode);
+
+
+G_DEFINE_TYPE (GimpOperationDissolve, gimp_operation_dissolve,
+               GIMP_TYPE_OPERATION_LAYER_MODE)
+
+
+static gint32 random_table[RANDOM_TABLE_SIZE];
+
+
+static void
+gimp_operation_dissolve_class_init (GimpOperationDissolveClass *klass)
+{
+  GeglOperationClass          *operation_class  = GEGL_OPERATION_CLASS (klass);
+  GimpOperationLayerModeClass *layer_mode_class = GIMP_OPERATION_LAYER_MODE_CLASS (klass);
+  GRand                       *gr;
+  gint                         i;
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name",        "gimp:dissolve",
+                                 "description", "GIMP dissolve mode operation",
+                                 "categories",  "compositors",
+                                 NULL);
+
+  layer_mode_class->process             = gimp_operation_dissolve_process;
+  layer_mode_class->get_affected_region = gimp_operation_dissolve_get_affected_region;
+
+  /* generate a table of random seeds */
+  gr = g_rand_new_with_seed (314159265);
+  for (i = 0; i < RANDOM_TABLE_SIZE; i++)
+    random_table[i] = g_rand_int (gr);
+
+  g_rand_free (gr);
+}
+
+static void
+gimp_operation_dissolve_init (GimpOperationDissolve *self)
+{
+}
+
+static gboolean
+gimp_operation_dissolve_process (GeglOperation       *op,
+                                 void                *in_p,
+                                 void                *layer_p,
+                                 void                *mask_p,
+                                 void                *out_p,
+                                 glong                samples,
+                                 const GeglRectangle *result,
+                                 gint                 level)
+{
+  GimpOperationLayerMode *layer_mode = (gpointer) op;
+  gfloat                 *in         = in_p;
+  gfloat                 *out        = out_p;
+  gfloat                 *layer      = layer_p;
+  gfloat                 *mask       = mask_p;
+  gfloat                  opacity    = layer_mode->opacity;
+  const gboolean          has_mask   = mask != NULL;
+  gint                    x, y;
+
+  for (y = result->y; y < result->y + result->height; y++)
+    {
+      GRand *gr = g_rand_new_with_seed (random_table[y % RANDOM_TABLE_SIZE]);
+
+      /* fast forward through the rows pseudo random sequence */
+      for (x = 0; x < result->x; x++)
+        g_rand_int (gr);
+
+      for (x = result->x; x < result->x + result->width; x++)
+        {
+          gfloat value = layer[ALPHA] * opacity * 255;
+
+          if (has_mask)
+            value *= *mask;
+
+          if (g_rand_int_range (gr, 0, 255) >= value)
+            {
+              out[0] = in[0];
+              out[1] = in[1];
+              out[2] = in[2];
+
+              if (layer_mode->real_composite_mode == GIMP_LAYER_COMPOSITE_UNION ||
+                  layer_mode->real_composite_mode == GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP)
+                {
+                  out[3] = in[3];
+                }
+              else
+                {
+                  out[3] = 0.0f;
+                }
+            }
+          else
+            {
+              out[0] = layer[0];
+              out[1] = layer[1];
+              out[2] = layer[2];
+
+              if (layer_mode->real_composite_mode == GIMP_LAYER_COMPOSITE_UNION ||
+                  layer_mode->real_composite_mode == GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER)
+                {
+                  out[3] = 1.0f;
+                }
+              else
+                {
+                  out[3] = in[3];
+                }
+            }
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+
+      g_rand_free (gr);
+    }
+
+  return TRUE;
+}
+
+static GimpLayerCompositeRegion
+gimp_operation_dissolve_get_affected_region (GimpOperationLayerMode *layer_mode)
+{
+  return GIMP_LAYER_COMPOSITE_REGION_SOURCE;
+}

app/operations/layer-modes/gimpoperationdissolve.h

@@ -0,0 +1,53 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationdissolve.h
+ * Copyright (C) 2012 Ville Sokk <ville.sokk@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_DISSOLVE_H__
+#define __GIMP_OPERATION_DISSOLVE_H__
+
+
+#include "gimpoperationlayermode.h"
+
+
+#define GIMP_TYPE_OPERATION_DISSOLVE            (gimp_operation_dissolve_get_type ())
+#define GIMP_OPERATION_DISSOLVE(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_OPERATION_DISSOLVE, GimpOperationDissolve))
+#define GIMP_OPERATION_DISSOLVE_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  GIMP_TYPE_OPERATION_DISSOLVE, GimpOperationDissolveClass))
+#define GIMP_IS_OPERATION_DISSOLVE(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_OPERATION_DISSOLVE))
+#define GIMP_IS_OPERATION_DISSOLVE_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  GIMP_TYPE_OPERATION_DISSOLVE))
+#define GIMP_OPERATION_DISSOLVE_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  GIMP_TYPE_OPERATION_DISSOLVE, GimpOperationDissolveClass))
+
+
+typedef struct _GimpOperationDissolve      GimpOperationDissolve;
+typedef struct _GimpOperationDissolveClass GimpOperationDissolveClass;
+
+struct _GimpOperationDissolveClass
+{
+  GimpOperationLayerModeClass parent_class;
+};
+
+struct _GimpOperationDissolve
+{
+  GimpOperationLayerMode parent_instance;
+};
+
+
+GType   gimp_operation_dissolve_get_type (void) G_GNUC_CONST;
+
+
+#endif /* __GIMP_OPERATION_DISSOLVE_H__ */

app/operations/layer-modes/gimpoperationerase.c

@@ -0,0 +1,214 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationerase.c
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *               2012 Ville Sokk <ville.sokk@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+
+#include "../operations-types.h"
+
+#include "gimpoperationerase.h"
+
+
+static gboolean   gimp_operation_erase_process (GeglOperation       *op,
+                                                void                *in,
+                                                void                *layer,
+                                                void                *mask,
+                                                void                *out,
+                                                glong                samples,
+                                                const GeglRectangle *roi,
+                                                gint                 level);
+
+
+G_DEFINE_TYPE (GimpOperationErase, gimp_operation_erase,
+               GIMP_TYPE_OPERATION_LAYER_MODE)
+
+
+static void
+gimp_operation_erase_class_init (GimpOperationEraseClass *klass)
+{
+  GeglOperationClass          *operation_class  = GEGL_OPERATION_CLASS (klass);
+  GimpOperationLayerModeClass *layer_mode_class = GIMP_OPERATION_LAYER_MODE_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name",        "gimp:erase",
+                                 "description", "GIMP erase mode operation",
+                                 NULL);
+
+  layer_mode_class->process = gimp_operation_erase_process;
+}
+
+static void
+gimp_operation_erase_init (GimpOperationErase *self)
+{
+}
+
+static gboolean
+gimp_operation_erase_process (GeglOperation       *op,
+                              void                *in_p,
+                              void                *layer_p,
+                              void                *mask_p,
+                              void                *out_p,
+                              glong                samples,
+                              const GeglRectangle *roi,
+                              gint                 level)
+{
+  GimpOperationLayerMode *layer_mode = (gpointer) op;
+  gfloat                 *in         = in_p;
+  gfloat                 *out        = out_p;
+  gfloat                 *layer      = layer_p;
+  gfloat                 *mask       = mask_p;
+  gfloat                  opacity    = layer_mode->opacity;
+  const gboolean          has_mask   = mask != NULL;
+
+  switch (layer_mode->real_composite_mode)
+    {
+    case GIMP_LAYER_COMPOSITE_UNION:
+      while (samples--)
+        {
+          gfloat layer_alpha;
+          gfloat new_alpha;
+          gint   b;
+
+          layer_alpha = layer[ALPHA] * opacity;
+
+          if (has_mask)
+            layer_alpha *= (*mask);
+
+          new_alpha = in[ALPHA] + layer_alpha - 2.0f * in[ALPHA] * layer_alpha;
+
+          if (new_alpha != 0.0f)
+            {
+              gfloat ratio;
+
+              ratio = (1.0f - in[ALPHA]) * layer_alpha / new_alpha;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = ratio * layer[b] + (1.0f - ratio) * in[b];
+                }
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask ++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+    case GIMP_LAYER_COMPOSITE_AUTO:
+      while (samples--)
+        {
+          gfloat layer_alpha;
+          gfloat new_alpha;
+          gint   b;
+
+          layer_alpha = layer[ALPHA] * opacity;
+
+          if (has_mask)
+            layer_alpha *= (*mask);
+
+          new_alpha = (1.0f - layer_alpha) * in[ALPHA];
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b];
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask ++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+      while (samples--)
+        {
+          gfloat        layer_alpha;
+          gfloat        new_alpha;
+          const gfloat *src;
+          gint          b;
+
+          layer_alpha = layer[ALPHA] * opacity;
+
+          if (has_mask)
+            layer_alpha *= (*mask);
+
+          new_alpha = (1.0f - in[ALPHA]) * layer_alpha;
+
+          src = layer;
+
+          if (new_alpha == 0.0f)
+            src = in;
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = src[b];
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask ++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_INTERSECTION:
+      while (samples--)
+        {
+          gint b;
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b];
+            }
+
+          out[ALPHA] = 0.0f;
+
+          in    += 4;
+          out   += 4;
+        }
+      break;
+    }
+
+  return TRUE;
+}

app/operations/layer-modes/gimpoperationerase.h

@@ -0,0 +1,53 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationerase.h
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_ERASE_H__
+#define __GIMP_OPERATION_ERASE_H__
+
+
+#include "gimpoperationlayermode.h"
+
+
+#define GIMP_TYPE_OPERATION_ERASE            (gimp_operation_erase_get_type ())
+#define GIMP_OPERATION_ERASE(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_OPERATION_ERASE, GimpOperationErase))
+#define GIMP_OPERATION_ERASE_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  GIMP_TYPE_OPERATION_ERASE, GimpOperationEraseClass))
+#define GIMP_IS_OPERATION_ERASE(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_OPERATION_ERASE))
+#define GIMP_IS_OPERATION_ERASE_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  GIMP_TYPE_OPERATION_ERASE))
+#define GIMP_OPERATION_ERASE_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  GIMP_TYPE_OPERATION_ERASE, GimpOperationEraseClass))
+
+
+typedef struct _GimpOperationErase      GimpOperationErase;
+typedef struct _GimpOperationEraseClass GimpOperationEraseClass;
+
+struct _GimpOperationErase
+{
+  GimpOperationLayerMode  parent_instance;
+};
+
+struct _GimpOperationEraseClass
+{
+  GimpOperationLayerModeClass  parent_class;
+};
+
+
+GType   gimp_operation_erase_get_type (void) G_GNUC_CONST;
+
+
+#endif /* __GIMP_OPERATION_ERASE_MODE_H__ */

app/operations/layer-modes/gimpoperationlayermode-blend.h

@@ -0,0 +1,167 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationlayermode-blend.h
+ * Copyright (C) 2017 Michael Natterer <mitch@gimp.org>
+ *               2017 Øyvind Kolås <pippin@gimp.org>
+ *               2017 Ell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; withcomp even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_LAYER_MODE_BLEND_H__
+#define __GIMP_OPERATION_LAYER_MODE_BLEND_H__
+
+
+/*  nonsubtractive blend functions  */
+
+void gimp_operation_layer_mode_blend_addition          (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_burn              (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_darken_only       (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_difference        (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_divide            (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_dodge             (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_exclusion         (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_grain_extract     (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_grain_merge       (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_hard_mix          (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_hardlight         (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_hsl_color         (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_hsv_hue           (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_hsv_saturation    (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_hsv_value         (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_lch_chroma        (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_lch_color         (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_lch_hue           (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_lch_lightness     (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_lighten_only      (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_linear_burn       (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_linear_light      (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_luma_darken_only  (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_luma_lighten_only (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_luminance         (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_multiply          (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_overlay           (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_pin_light         (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_screen            (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_softlight         (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_subtract          (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+void gimp_operation_layer_mode_blend_vivid_light       (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+
+
+/*  subtractive blend functions  */
+
+void gimp_operation_layer_mode_blend_color_erase       (const gfloat *in,
+                                                        const gfloat *layer,
+                                                        gfloat       *comp,
+                                                        gint          samples);
+
+
+#endif /* __GIMP_OPERATION_LAYER_MODE_BLEND_H__ */

app/operations/layer-modes/gimpoperationlayermode-composite-sse2.c

@@ -0,0 +1,105 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationlayermode-composite-sse2.c
+ * Copyright (C) 2017 Michael Natterer <mitch@gimp.org>
+ *               2017 Øyvind Kolås <pippin@gimp.org>
+ *               2017 Ell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+#include <cairo.h>
+#include <gdk-pixbuf/gdk-pixbuf.h>
+
+#include "../operations-types.h"
+
+#include "gimpoperationlayermode-composite.h"
+
+
+#if COMPILE_SSE2_INTRINISICS
+
+/* SSE2 */
+#include <emmintrin.h>
+
+
+/*  non-subtractive compositing functions.  these functions expect comp[ALPHA]
+ *  to be the same as layer[ALPHA].  when in[ALPHA] or layer[ALPHA] are zero,
+ *  the value of comp[RED..BLUE] is unconstrained (in particular, it may be
+ *  NaN).
+ */
+
+
+void
+gimp_operation_layer_mode_composite_clip_to_backdrop_sse2 (const gfloat *in,
+                                                           const gfloat *layer,
+                                                           const gfloat *comp,
+                                                           const gfloat *mask,
+                                                           gfloat        opacity,
+                                                           gfloat       *out,
+                                                           gint          samples)
+{
+  if ((((uintptr_t)in)   | /* alignment check */
+       ((uintptr_t)comp) |
+       ((uintptr_t)out)   ) & 0x0F)
+    {
+      gimp_operation_layer_mode_composite_clip_to_backdrop (in, layer, comp,
+                                                            mask, opacity, out,
+                                                            samples);
+    }
+  else
+    {
+      const __v4sf *v_in      = (const __v4sf*) in;
+      const __v4sf *v_comp    = (const __v4sf*) comp;
+            __v4sf *v_out     = (__v4sf*) out;
+      const __v4sf  v_one     =  _mm_set1_ps (1.0f);
+      const __v4sf  v_opacity =  _mm_set1_ps (opacity);
+
+      while (samples--)
+        {
+          __v4sf alpha, rgba_in, rgba_comp;
+
+          rgba_in   = *v_in ++;
+          rgba_comp = *v_comp++;
+
+          alpha = (__v4sf)_mm_shuffle_epi32((__m128i)rgba_comp,_MM_SHUFFLE(3,3,3,3)) * v_opacity;
+
+          if (mask)
+            {
+              alpha = alpha * _mm_set1_ps (*mask++);
+            }
+
+          if (rgba_in[ALPHA] != 0.0f && _mm_ucomineq_ss (alpha, _mm_setzero_ps ()))
+            {
+              __v4sf out_pixel, out_pixel_rbaa, out_alpha;
+
+              out_alpha      = (__v4sf)_mm_shuffle_epi32((__m128i)rgba_in,_MM_SHUFFLE(3,3,3,3));
+              out_pixel      = rgba_comp * alpha + rgba_in * (v_one - alpha);
+              out_pixel_rbaa = _mm_shuffle_ps (out_pixel, out_alpha, _MM_SHUFFLE (3, 3, 2, 0));
+              out_pixel      = _mm_shuffle_ps (out_pixel, out_pixel_rbaa, _MM_SHUFFLE (2, 1, 1, 0));
+
+              *v_out++ = out_pixel;
+            }
+          else
+            {
+              *v_out ++ = rgba_in;
+            }
+        }
+    }
+}
+
+#endif /* COMPILE_SSE2_INTRINISICS */

app/operations/layer-modes/gimpoperationlayermode-composite.c

@@ -0,0 +1,434 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationlayermode-composite.c
+ * Copyright (C) 2017 Michael Natterer <mitch@gimp.org>
+ *               2017 Øyvind Kolås <pippin@gimp.org>
+ *               2017 Ell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+#include <cairo.h>
+#include <gdk-pixbuf/gdk-pixbuf.h>
+
+#include "../operations-types.h"
+
+#include "gimpoperationlayermode-composite.h"
+
+
+/*  non-subtractive compositing functions.  these functions expect comp[ALPHA]
+ *  to be the same as layer[ALPHA].  when in[ALPHA] or layer[ALPHA] are zero,
+ *  the value of comp[RED..BLUE] is unconstrained (in particular, it may be
+ *  NaN).
+ */
+
+
+void
+gimp_operation_layer_mode_composite_union (const gfloat *in,
+                                           const gfloat *layer,
+                                           const gfloat *comp,
+                                           const gfloat *mask,
+                                           gfloat        opacity,
+                                           gfloat       *out,
+                                           gint          samples)
+{
+  while (samples--)
+    {
+      gfloat new_alpha;
+      gfloat in_alpha    = in[ALPHA];
+      gfloat layer_alpha = layer[ALPHA] * opacity;
+
+      if (mask)
+        layer_alpha *= *mask;
+
+      new_alpha = layer_alpha + (1.0f - layer_alpha) * in_alpha;
+
+      if (layer_alpha == 0.0f || new_alpha == 0.0f)
+        {
+          out[RED]   = in[RED];
+          out[GREEN] = in[GREEN];
+          out[BLUE]  = in[BLUE];
+        }
+      else if (in_alpha == 0.0f)
+        {
+          out[RED]   = layer[RED];
+          out[GREEN] = layer[GREEN];
+          out[BLUE]  = layer[BLUE];
+        }
+      else
+        {
+          gfloat ratio = layer_alpha / new_alpha;
+          gint   b;
+
+          for (b = RED; b < ALPHA; b++)
+            out[b] = ratio * (in_alpha * (comp[b] - layer[b]) + layer[b] - in[b]) + in[b];
+        }
+
+      out[ALPHA] = new_alpha;
+
+      in    += 4;
+      layer += 4;
+      comp  += 4;
+      out   += 4;
+
+      if (mask)
+        mask++;
+    }
+}
+
+void
+gimp_operation_layer_mode_composite_clip_to_backdrop (const gfloat *in,
+                                                      const gfloat *layer,
+                                                      const gfloat *comp,
+                                                      const gfloat *mask,
+                                                      gfloat        opacity,
+                                                      gfloat       *out,
+                                                      gint          samples)
+{
+  while (samples--)
+    {
+      gfloat layer_alpha = comp[ALPHA] * opacity;
+
+      if (mask)
+        layer_alpha *= *mask;
+
+      if (in[ALPHA] == 0.0f || layer_alpha == 0.0f)
+        {
+          out[RED]   = in[RED];
+          out[GREEN] = in[GREEN];
+          out[BLUE]  = in[BLUE];
+        }
+      else
+        {
+          gint b;
+
+          for (b = RED; b < ALPHA; b++)
+            out[b] = comp[b] * layer_alpha + in[b] * (1.0f - layer_alpha);
+        }
+
+      out[ALPHA] = in[ALPHA];
+
+      in   += 4;
+      comp += 4;
+      out  += 4;
+
+      if (mask)
+        mask++;
+    }
+}
+
+void
+gimp_operation_layer_mode_composite_clip_to_layer (const gfloat *in,
+                                                   const gfloat *layer,
+                                                   const gfloat *comp,
+                                                   const gfloat *mask,
+                                                   gfloat        opacity,
+                                                   gfloat       *out,
+                                                   gint          samples)
+{
+  while (samples--)
+    {
+      gfloat layer_alpha = layer[ALPHA] * opacity;
+
+      if (mask)
+        layer_alpha *= *mask;
+
+      if (layer_alpha == 0.0f)
+        {
+          out[RED]   = in[RED];
+          out[GREEN] = in[GREEN];
+          out[BLUE]  = in[BLUE];
+        }
+      else if (in[ALPHA] == 0.0f)
+        {
+          out[RED]   = layer[RED];
+          out[GREEN] = layer[GREEN];
+          out[BLUE]  = layer[BLUE];
+        }
+      else
+        {
+          gint b;
+
+          for (b = RED; b < ALPHA; b++)
+            out[b] = comp[b] * in[ALPHA] + layer[b] * (1.0f - in[ALPHA]);
+        }
+
+      out[ALPHA] = layer_alpha;
+
+      in    += 4;
+      layer += 4;
+      comp  += 4;
+      out   += 4;
+
+      if (mask)
+        mask++;
+    }
+}
+
+void
+gimp_operation_layer_mode_composite_intersection (const gfloat *in,
+                                                  const gfloat *layer,
+                                                  const gfloat *comp,
+                                                  const gfloat *mask,
+                                                  gfloat        opacity,
+                                                  gfloat       *out,
+                                                  gint          samples)
+{
+  while (samples--)
+    {
+      gfloat new_alpha = in[ALPHA] * comp[ALPHA] * opacity;
+
+      if (mask)
+        new_alpha *= *mask;
+
+      if (new_alpha == 0.0f)
+        {
+          out[RED]   = in[RED];
+          out[GREEN] = in[GREEN];
+          out[BLUE]  = in[BLUE];
+        }
+      else
+        {
+          out[RED]   = comp[RED];
+          out[GREEN] = comp[GREEN];
+          out[BLUE]  = comp[BLUE];
+        }
+
+      out[ALPHA] = new_alpha;
+
+      in   += 4;
+      comp += 4;
+      out  += 4;
+
+      if (mask)
+        mask++;
+    }
+}
+
+/*  subtractive compositing functions.  these functions expect comp[ALPHA] to
+ *  specify the modified alpha of the overlapping content, as a fraction of the
+ *  original overlapping content (i.e., an alpha of 1.0 specifies that no
+ *  content is subtracted.)  when in[ALPHA] or layer[ALPHA] are zero, the value
+ *  of comp[RED..BLUE] is unconstrained (in particular, it may be NaN).
+ */
+
+void
+gimp_operation_layer_mode_composite_union_sub (const gfloat *in,
+                                               const gfloat *layer,
+                                               const gfloat *comp,
+                                               const gfloat *mask,
+                                               gfloat        opacity,
+                                               gfloat       *out,
+                                               gint          samples)
+{
+  while (samples--)
+    {
+      gfloat in_alpha    = in[ALPHA];
+      gfloat layer_alpha = layer[ALPHA] * opacity;
+      gfloat comp_alpha  = comp[ALPHA];
+      gfloat new_alpha;
+
+      if (mask)
+        layer_alpha *= *mask;
+
+      new_alpha = in_alpha + layer_alpha -
+                  (2.0f - comp_alpha) * in_alpha * layer_alpha;
+
+      if (layer_alpha == 0.0f || new_alpha == 0.0f)
+        {
+          out[RED]   = in[RED];
+          out[GREEN] = in[GREEN];
+          out[BLUE]  = in[BLUE];
+        }
+      else if (in_alpha == 0.0f)
+        {
+          out[RED]   = layer[RED];
+          out[GREEN] = layer[GREEN];
+          out[BLUE]  = layer[BLUE];
+        }
+      else
+        {
+          gfloat ratio       = in_alpha / new_alpha;
+          gfloat layer_coeff = 1.0f / in_alpha - 1.0f;
+          gint   b;
+
+          for (b = RED; b < ALPHA; b++)
+            out[b] = ratio * (layer_alpha * (comp_alpha * comp[b] + layer_coeff * layer[b] - in[b]) + in[b]);
+        }
+
+      out[ALPHA] = new_alpha;
+
+      in    += 4;
+      layer += 4;
+      comp  += 4;
+      out   += 4;
+
+      if (mask)
+        mask++;
+    }
+}
+
+void
+gimp_operation_layer_mode_composite_clip_to_backdrop_sub (const gfloat *in,
+                                                          const gfloat *layer,
+                                                          const gfloat *comp,
+                                                          const gfloat *mask,
+                                                          gfloat        opacity,
+                                                          gfloat       *out,
+                                                          gint          samples)
+{
+  while (samples--)
+    {
+      gfloat layer_alpha = layer[ALPHA] * opacity;
+      gfloat comp_alpha  = comp[ALPHA];
+      gfloat new_alpha;
+
+      if (mask)
+        layer_alpha *= *mask;
+
+      comp_alpha *= layer_alpha;
+
+      new_alpha = 1.0f - layer_alpha + comp_alpha;
+
+      if (in[ALPHA] == 0.0f || comp_alpha == 0.0f)
+        {
+          out[RED]   = in[RED];
+          out[GREEN] = in[GREEN];
+          out[BLUE]  = in[BLUE];
+        }
+      else
+        {
+          gfloat ratio = comp_alpha / new_alpha;
+          gint   b;
+
+          for (b = RED; b < ALPHA; b++)
+            out[b] = comp[b] * ratio + in[b] * (1.0f - ratio);
+        }
+
+      new_alpha *= in[ALPHA];
+
+      out[ALPHA] = new_alpha;
+
+      in    += 4;
+      layer += 4;
+      comp  += 4;
+      out   += 4;
+
+      if (mask)
+        mask++;
+    }
+}
+
+void
+gimp_operation_layer_mode_composite_clip_to_layer_sub (const gfloat *in,
+                                                       const gfloat *layer,
+                                                       const gfloat *comp,
+                                                       const gfloat *mask,
+                                                       gfloat        opacity,
+                                                       gfloat       *out,
+                                                       gint          samples)
+{
+  while (samples--)
+    {
+      gfloat in_alpha    = in[ALPHA];
+      gfloat layer_alpha = layer[ALPHA] * opacity;
+      gfloat comp_alpha  = comp[ALPHA];
+      gfloat new_alpha;
+
+      if (mask)
+        layer_alpha *= *mask;
+
+      comp_alpha *= in_alpha;
+
+      new_alpha = 1.0f - in_alpha + comp_alpha;
+
+      if (layer_alpha == 0.0f)
+        {
+          out[RED]   = in[RED];
+          out[GREEN] = in[GREEN];
+          out[BLUE]  = in[BLUE];
+        }
+      else if (in_alpha == 0.0f)
+        {
+          out[RED]   = layer[RED];
+          out[GREEN] = layer[GREEN];
+          out[BLUE]  = layer[BLUE];
+        }
+      else
+        {
+          gfloat ratio = comp_alpha / new_alpha;
+          gint   b;
+
+          for (b = RED; b < ALPHA; b++)
+            out[b] = comp[b] * ratio + layer[b] * (1.0f - ratio);
+        }
+
+      new_alpha *= layer_alpha;
+
+      out[ALPHA] = new_alpha;
+
+      in    += 4;
+      layer += 4;
+      comp  += 4;
+      out   += 4;
+
+      if (mask)
+        mask++;
+    }
+}
+
+void
+gimp_operation_layer_mode_composite_intersection_sub (const gfloat *in,
+                                                      const gfloat *layer,
+                                                      const gfloat *comp,
+                                                      const gfloat *mask,
+                                                      gfloat        opacity,
+                                                      gfloat       *out,
+                                                      gint          samples)
+{
+  while (samples--)
+    {
+      gfloat new_alpha = in[ALPHA] * layer[ALPHA] * comp[ALPHA] * opacity;
+
+      if (mask)
+        new_alpha *= *mask;
+
+      if (new_alpha == 0.0f)
+        {
+          out[RED]   = in[RED];
+          out[GREEN] = in[GREEN];
+          out[BLUE]  = in[BLUE];
+        }
+      else
+        {
+          out[RED]   = comp[RED];
+          out[GREEN] = comp[GREEN];
+          out[BLUE]  = comp[BLUE];
+        }
+
+      out[ALPHA] = new_alpha;
+
+      in    += 4;
+      layer += 4;
+      comp  += 4;
+      out   += 4;
+
+      if (mask)
+        mask++;
+    }
+}

app/operations/layer-modes/gimpoperationlayermode-composite.h

@@ -0,0 +1,98 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationlayermode-composite.h
+ * Copyright (C) 2017 Michael Natterer <mitch@gimp.org>
+ *               2017 Øyvind Kolås <pippin@gimp.org>
+ *               2017 Ell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_LAYER_MODE_COMPOSITE_H__
+#define __GIMP_OPERATION_LAYER_MODE_COMPOSITE_H__
+
+
+void gimp_operation_layer_mode_composite_union                 (const gfloat        *in,
+                                                                const gfloat        *layer,
+                                                                const gfloat        *comp,
+                                                                const gfloat        *mask,
+                                                                gfloat               opacity,
+                                                                gfloat              *out,
+                                                                gint                 samples);
+void gimp_operation_layer_mode_composite_clip_to_backdrop      (const gfloat        *in,
+                                                                const gfloat        *layer,
+                                                                const gfloat        *comp,
+                                                                const gfloat        *mask,
+                                                                gfloat               opacity,
+                                                                gfloat              *out,
+                                                                gint                 samples);
+void gimp_operation_layer_mode_composite_clip_to_layer         (const gfloat        *in,
+                                                                const gfloat        *layer,
+                                                                const gfloat        *comp,
+                                                                const gfloat        *mask,
+                                                                gfloat               opacity,
+                                                                gfloat              *out,
+                                                                gint                 samples);
+void gimp_operation_layer_mode_composite_intersection          (const gfloat        *in,
+                                                                const gfloat        *layer,
+                                                                const gfloat        *comp,
+                                                                const gfloat        *mask,
+                                                                gfloat               opacity,
+                                                                gfloat              *out,
+                                                                gint                 samples);
+
+void gimp_operation_layer_mode_composite_union_sub             (const gfloat        *in,
+                                                                const gfloat        *layer,
+                                                                const gfloat        *comp,
+                                                                const gfloat        *mask,
+                                                                gfloat               opacity,
+                                                                gfloat              *out,
+                                                                gint                 samples);
+void gimp_operation_layer_mode_composite_clip_to_backdrop_sub  (const gfloat        *in,
+                                                                const gfloat        *layer,
+                                                                const gfloat        *comp,
+                                                                const gfloat        *mask,
+                                                                gfloat               opacity,
+                                                                gfloat              *out,
+                                                                gint                 samples);
+void gimp_operation_layer_mode_composite_clip_to_layer_sub     (const gfloat        *in,
+                                                                const gfloat        *layer,
+                                                                const gfloat        *comp,
+                                                                const gfloat        *mask,
+                                                                gfloat               opacity,
+                                                                gfloat              *out,
+                                                                gint                 samples);
+void gimp_operation_layer_mode_composite_intersection_sub      (const gfloat        *in,
+                                                                const gfloat        *layer,
+                                                                const gfloat        *comp,
+                                                                const gfloat        *mask,
+                                                                gfloat               opacity,
+                                                                gfloat              *out,
+                                                                gint                 samples);
+
+#if COMPILE_SSE2_INTRINISICS
+
+void gimp_operation_layer_mode_composite_clip_to_backdrop_sse2 (const gfloat        *in,
+                                                                const gfloat        *layer,
+                                                                const gfloat        *comp,
+                                                                const gfloat        *mask,
+                                                                gfloat               opacity,
+                                                                gfloat              *out,
+                                                                gint                 samples);
+
+#endif /* COMPILE_SSE2_INTRINISICS */
+
+
+#endif /* __GIMP_OPERATION_LAYER_MODE_COMPOSITE_H__ */

app/operations/layer-modes/gimpoperationlayermode.c

@@ -0,0 +1,812 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationlayermode.c
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ * Copyright (C) 2008 Martin Nordholts <martinn@svn.gnome.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+#include <cairo.h>
+#include <gdk-pixbuf/gdk-pixbuf.h>
+
+#include "libgimpbase/gimpbase.h"
+
+#include "../operations-types.h"
+
+#include "gimp-layer-modes.h"
+#include "gimpoperationlayermode.h"
+#include "gimpoperationlayermode-composite.h"
+
+
+/* the maximum number of samples to process in one go.  used to limit
+ * the size of the buffers we allocate on the stack.
+ */
+#define GIMP_COMPOSITE_BLEND_MAX_SAMPLES ((1 << 19) /* 0.5 MiB */  /      \
+                                          16 /* bytes per pixel */ /      \
+                                          2  /* max number of buffers */)
+
+/* number of consecutive unblended samples (whose source or destination alpha
+ * is zero) above which to split the blending process, in order to avoid
+ * performing too many unnecessary conversions.
+ */
+#define GIMP_COMPOSITE_BLEND_SPLIT_THRESHOLD 32
+
+
+enum
+{
+  PROP_0,
+  PROP_LAYER_MODE,
+  PROP_OPACITY,
+  PROP_BLEND_SPACE,
+  PROP_COMPOSITE_SPACE,
+  PROP_COMPOSITE_MODE
+};
+
+
+typedef void (* CompositeFunc) (const gfloat *in,
+                                const gfloat *layer,
+                                const gfloat *comp,
+                                const gfloat *mask,
+                                float         opacity,
+                                gfloat       *out,
+                                gint          samples);
+
+
+static void       gimp_operation_layer_mode_set_property   (GObject                *object,
+                                                            guint                   property_id,
+                                                            const GValue           *value,
+                                                            GParamSpec             *pspec);
+static void       gimp_operation_layer_mode_get_property   (GObject                *object,
+                                                            guint                   property_id,
+                                                            GValue                 *value,
+                                                            GParamSpec             *pspec);
+
+static void       gimp_operation_layer_mode_prepare        (GeglOperation          *operation);
+static gboolean   gimp_operation_layer_mode_parent_process (GeglOperation          *operation,
+                                                            GeglOperationContext   *context,
+                                                            const gchar            *output_prop,
+                                                            const GeglRectangle    *result,
+                                                            gint                    level);
+
+static gboolean   gimp_operation_layer_mode_process        (GeglOperation          *operation,
+                                                            void                   *in,
+                                                            void                   *layer,
+                                                            void                   *mask,
+                                                            void                   *out,
+                                                            glong                   samples,
+                                                            const GeglRectangle    *roi,
+                                                            gint                    level);
+
+static gboolean   gimp_operation_layer_mode_real_process   (GeglOperation          *operation,
+                                                            void                   *in,
+                                                            void                   *layer,
+                                                            void                   *mask,
+                                                            void                   *out,
+                                                            glong                   samples,
+                                                            const GeglRectangle    *roi,
+                                                            gint                    level);
+
+static gboolean   process_last_node                        (GeglOperation       *operation,
+                                                            void                *in,
+                                                            void                *layer,
+                                                            void                *mask,
+                                                            void                *out,
+                                                            glong                samples,
+                                                            const GeglRectangle *roi,
+                                                            gint                 level);
+
+
+G_DEFINE_TYPE (GimpOperationLayerMode, gimp_operation_layer_mode,
+               GEGL_TYPE_OPERATION_POINT_COMPOSER3)
+
+#define parent_class gimp_operation_layer_mode_parent_class
+
+
+static const Babl *gimp_layer_color_space_fish[3 /* from */][3 /* to */];
+
+static CompositeFunc composite_union                = gimp_operation_layer_mode_composite_union;
+static CompositeFunc composite_clip_to_backdrop     = gimp_operation_layer_mode_composite_clip_to_backdrop;
+static CompositeFunc composite_clip_to_layer        = gimp_operation_layer_mode_composite_clip_to_layer;
+static CompositeFunc composite_intersection         = gimp_operation_layer_mode_composite_intersection;
+
+static CompositeFunc composite_union_sub            = gimp_operation_layer_mode_composite_union_sub;
+static CompositeFunc composite_clip_to_backdrop_sub = gimp_operation_layer_mode_composite_clip_to_backdrop_sub;
+static CompositeFunc composite_clip_to_layer_sub    = gimp_operation_layer_mode_composite_clip_to_layer_sub;
+static CompositeFunc composite_intersection_sub     = gimp_operation_layer_mode_composite_intersection_sub;
+
+
+static void
+gimp_operation_layer_mode_class_init (GimpOperationLayerModeClass *klass)
+{
+  GObjectClass                     *object_class          = G_OBJECT_CLASS (klass);
+  GeglOperationClass               *operation_class       = GEGL_OPERATION_CLASS (klass);
+  GeglOperationPointComposer3Class *point_composer3_class = GEGL_OPERATION_POINT_COMPOSER3_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name", "gimp:layer-mode", NULL);
+
+  object_class->set_property     = gimp_operation_layer_mode_set_property;
+  object_class->get_property     = gimp_operation_layer_mode_get_property;
+
+  operation_class->prepare       = gimp_operation_layer_mode_prepare;
+  operation_class->process       = gimp_operation_layer_mode_parent_process;
+
+  point_composer3_class->process = gimp_operation_layer_mode_process;
+
+  klass->process                 = gimp_operation_layer_mode_real_process;
+  klass->get_affected_region     = NULL;
+
+  g_object_class_install_property (object_class, PROP_LAYER_MODE,
+                                   g_param_spec_enum ("layer-mode",
+                                                      NULL, NULL,
+                                                      GIMP_TYPE_LAYER_MODE,
+                                                      GIMP_LAYER_MODE_NORMAL,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_OPACITY,
+                                   g_param_spec_double ("opacity",
+                                                        NULL, NULL,
+                                                        0.0, 1.0, 1.0,
+                                                        GIMP_PARAM_READWRITE |
+                                                        G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_BLEND_SPACE,
+                                   g_param_spec_enum ("blend-space",
+                                                      NULL, NULL,
+                                                      GIMP_TYPE_LAYER_COLOR_SPACE,
+                                                      GIMP_LAYER_COLOR_SPACE_RGB_LINEAR,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+
+  g_object_class_install_property (object_class, PROP_COMPOSITE_SPACE,
+                                   g_param_spec_enum ("composite-space",
+                                                      NULL, NULL,
+                                                      GIMP_TYPE_LAYER_COLOR_SPACE,
+                                                      GIMP_LAYER_COLOR_SPACE_RGB_LINEAR,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_COMPOSITE_MODE,
+                                   g_param_spec_enum ("composite-mode",
+                                                      NULL, NULL,
+                                                      GIMP_TYPE_LAYER_COMPOSITE_MODE,
+                                                      GIMP_LAYER_COMPOSITE_UNION,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_RGB_LINEAR     - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_RGB_PERCEPTUAL - 1] =
+      babl_fish ("RGBA float", "R'G'B'A float");
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_RGB_LINEAR     - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_LAB            - 1] =
+      babl_fish ("RGBA float", "CIE Lab alpha float");
+
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_RGB_PERCEPTUAL - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_RGB_LINEAR     - 1] =
+      babl_fish ("R'G'B'A float", "RGBA float");
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_RGB_PERCEPTUAL - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_LAB            - 1] =
+      babl_fish ("R'G'B'A float", "CIE Lab alpha float");
+
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_LAB            - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_RGB_LINEAR     - 1] =
+      babl_fish ("CIE Lab alpha float", "RGBA float");
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_LAB            - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_RGB_PERCEPTUAL - 1] =
+      babl_fish ("CIE Lab alpha float", "R'G'B'A float");
+
+#if COMPILE_SSE2_INTRINISICS
+  if (gimp_cpu_accel_get_support () & GIMP_CPU_ACCEL_X86_SSE2)
+    composite_clip_to_backdrop = gimp_operation_layer_mode_composite_clip_to_backdrop_sse2;
+#endif
+}
+
+static void
+gimp_operation_layer_mode_init (GimpOperationLayerMode *self)
+{
+}
+
+static void
+gimp_operation_layer_mode_set_property (GObject      *object,
+                                        guint         property_id,
+                                        const GValue *value,
+                                        GParamSpec   *pspec)
+{
+  GimpOperationLayerMode *self = GIMP_OPERATION_LAYER_MODE (object);
+
+  switch (property_id)
+    {
+    case PROP_LAYER_MODE:
+      self->layer_mode = g_value_get_enum (value);
+      break;
+
+    case PROP_OPACITY:
+      self->opacity = g_value_get_double (value);
+      break;
+
+    case PROP_BLEND_SPACE:
+      self->blend_space = g_value_get_enum (value);
+      break;
+
+    case PROP_COMPOSITE_SPACE:
+      self->composite_space = g_value_get_enum (value);
+      break;
+
+    case PROP_COMPOSITE_MODE:
+      self->composite_mode = g_value_get_enum (value);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+      break;
+    }
+}
+
+static void
+gimp_operation_layer_mode_get_property (GObject    *object,
+                                        guint       property_id,
+                                        GValue     *value,
+                                        GParamSpec *pspec)
+{
+  GimpOperationLayerMode *self = GIMP_OPERATION_LAYER_MODE (object);
+
+  switch (property_id)
+    {
+    case PROP_LAYER_MODE:
+      g_value_set_enum (value, self->layer_mode);
+      break;
+
+    case PROP_OPACITY:
+      g_value_set_double (value, self->opacity);
+      break;
+
+    case PROP_BLEND_SPACE:
+      g_value_set_enum (value, self->blend_space);
+      break;
+
+    case PROP_COMPOSITE_SPACE:
+      g_value_set_enum (value, self->composite_space);
+      break;
+
+    case PROP_COMPOSITE_MODE:
+      g_value_set_enum (value, self->composite_mode);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+      break;
+    }
+}
+
+static void
+gimp_operation_layer_mode_prepare (GeglOperation *operation)
+{
+  GimpOperationLayerMode *self = GIMP_OPERATION_LAYER_MODE (operation);
+  const GeglRectangle    *input_extent;
+  const Babl             *preferred_format;
+  const Babl             *format;
+
+  self->real_composite_mode = self->composite_mode;
+
+  if (self->real_composite_mode == GIMP_LAYER_COMPOSITE_AUTO)
+    {
+      self->real_composite_mode =
+        gimp_layer_mode_get_composite_mode (self->layer_mode);
+
+      g_warn_if_fail (self->real_composite_mode != GIMP_LAYER_COMPOSITE_AUTO);
+    }
+
+  self->function       = gimp_layer_mode_get_function       (self->layer_mode);
+  self->blend_function = gimp_layer_mode_get_blend_function (self->layer_mode);
+
+  input_extent = gegl_operation_source_get_bounding_box (operation, "input");
+
+  /* if the input pad has data, work as usual. */
+  if (input_extent && ! gegl_rectangle_is_empty (input_extent))
+    {
+      self->is_last_node = FALSE;
+
+      preferred_format = gegl_operation_get_source_format (operation, "input");
+    }
+  /* otherwise, we're the last node (corresponding to the bottom layer).
+   * in this case, we render the layer (as if) using UNION mode.
+   */
+  else
+    {
+      self->is_last_node = TRUE;
+
+      /* if the layer mode doesn't affect the source, use a shortcut
+       * function that only applies the opacity/mask to the layer.
+       */
+      if (! (gimp_operation_layer_mode_get_affected_region (self) &
+             GIMP_LAYER_COMPOSITE_REGION_SOURCE))
+        {
+          self->function = process_last_node;
+        }
+      /* otherwise, use the original process function, but force the
+       * composite mode to UNION.
+       */
+      else
+        {
+          self->real_composite_mode = GIMP_LAYER_COMPOSITE_UNION;
+        }
+
+      preferred_format = gegl_operation_get_source_format (operation, "aux");
+    }
+
+  format = gimp_layer_mode_get_format (self->layer_mode,
+                                       self->composite_space,
+                                       self->blend_space,
+                                       preferred_format);
+
+  gegl_operation_set_format (operation, "input",  format);
+  gegl_operation_set_format (operation, "output", format);
+  gegl_operation_set_format (operation, "aux",    format);
+  gegl_operation_set_format (operation, "aux2",   babl_format ("Y float"));
+}
+
+static gboolean
+gimp_operation_layer_mode_parent_process (GeglOperation        *operation,
+                                          GeglOperationContext *context,
+                                          const gchar          *output_prop,
+                                          const GeglRectangle  *result,
+                                          gint                  level)
+{
+  GimpOperationLayerMode   *point = GIMP_OPERATION_LAYER_MODE (operation);
+  GObject                  *input;
+  GObject                  *aux;
+  gboolean                  has_input;
+  gboolean                  has_aux;
+  GimpLayerCompositeRegion  included_region;
+
+  /* get the raw values.  this does not increase the reference count. */
+  input = gegl_operation_context_get_object (context, "input");
+  aux   = gegl_operation_context_get_object (context, "aux");
+
+  /* disregard 'input' if it's not included in the roi. */
+  has_input =
+    input &&
+    gegl_rectangle_intersect (NULL,
+                              gegl_buffer_get_extent (GEGL_BUFFER (input)),
+                              result);
+
+  /* disregard 'aux' if it's not included in the roi, or if it's fully
+   * transparent.
+   */
+  has_aux =
+    aux &&
+    point->opacity != 0.0 &&
+    gegl_rectangle_intersect (NULL,
+                              gegl_buffer_get_extent (GEGL_BUFFER (aux)),
+                              result);
+
+  if (point->is_last_node)
+    {
+      included_region = GIMP_LAYER_COMPOSITE_REGION_SOURCE;
+    }
+  else
+    {
+      included_region = gimp_layer_mode_get_included_region (point->layer_mode,
+                                                             point->composite_mode);
+    }
+
+  /* if there's no 'input' ... */
+  if (! has_input)
+    {
+      /* ... and there's 'aux', and the composite mode includes it (or we're
+       * the last node) ...
+       */
+      if (has_aux && (included_region & GIMP_LAYER_COMPOSITE_REGION_SOURCE))
+        {
+          GimpLayerCompositeRegion affected_region;
+
+          affected_region =
+            gimp_operation_layer_mode_get_affected_region (point);
+
+          /* ... and the op doesn't otherwise affect 'aux', or changes its
+           * alpha ...
+           */
+          if (! (affected_region & GIMP_LAYER_COMPOSITE_REGION_SOURCE) &&
+              point->opacity == 1.0                                    &&
+              ! gegl_operation_context_get_object (context, "aux2"))
+            {
+              /* pass 'aux' directly as output; */
+              gegl_operation_context_set_object (context, "output", aux);
+              return TRUE;
+            }
+
+          /* otherwise, if the op affects 'aux', or changes its alpha, process
+           * it even though there's no 'input';
+           */
+        }
+      /* otherwise, there's no 'aux', or the composite mode doesn't include it,
+       * and so ...
+       */
+      else
+        {
+          /* ... the output is empty. */
+          gegl_operation_context_set_object (context, "output", NULL);
+          return TRUE;
+        }
+    }
+  /* otherwise, if there's 'input' but no 'aux' ... */
+  else if (! has_aux)
+    {
+      /* ... and the composite mode includes 'input' ... */
+      if (included_region & GIMP_LAYER_COMPOSITE_REGION_DESTINATION)
+        {
+          GimpLayerCompositeRegion affected_region;
+
+          affected_region =
+            gimp_operation_layer_mode_get_affected_region (point);
+
+          /* ... and the op doesn't otherwise affect 'input' ... */
+          if (! (affected_region & GIMP_LAYER_COMPOSITE_REGION_DESTINATION))
+            {
+              /* pass 'input' directly as output; */
+              gegl_operation_context_set_object (context, "output", input);
+              return TRUE;
+            }
+
+          /* otherwise, if the op affects 'input', process it even though
+           * there's no 'aux';
+           */
+        }
+
+      /* otherwise, the output is fully transparent, but we process it anyway
+       * to maintain the 'input' color values.
+       */
+    }
+
+  /* FIXME: we don't actually handle the case where one of the inputs
+   * is NULL -- it'll just segfault.  'input' is not expected to be NULL,
+   * but 'aux' might be, currently.
+   */
+  if (! input || ! aux)
+    {
+      GObject *empty = G_OBJECT (gegl_buffer_new (NULL, NULL));
+
+      if (! input) gegl_operation_context_set_object (context, "input", empty);
+      if (! aux)   gegl_operation_context_set_object (context, "aux",   empty);
+
+      if (! input && ! aux)
+        gegl_object_set_has_forked (G_OBJECT (empty));
+
+      g_object_unref (empty);
+    }
+
+  /* chain up, which will create the needed buffers for our actual
+   * process function
+   */
+  return GEGL_OPERATION_CLASS (parent_class)->process (operation, context,
+                                                       output_prop, result,
+                                                       level);
+}
+
+static gboolean
+gimp_operation_layer_mode_process (GeglOperation       *operation,
+                                   void                *in,
+                                   void                *layer,
+                                   void                *mask,
+                                   void                *out,
+                                   glong                samples,
+                                   const GeglRectangle *roi,
+                                   gint                 level)
+{
+  return ((GimpOperationLayerMode *) operation)->function (
+    operation, in, layer, mask, out, samples, roi, level);
+}
+
+static gboolean
+gimp_operation_layer_mode_real_process (GeglOperation       *operation,
+                                        void                *in_p,
+                                        void                *layer_p,
+                                        void                *mask_p,
+                                        void                *out_p,
+                                        glong                samples,
+                                        const GeglRectangle *roi,
+                                        gint                 level)
+{
+  GimpOperationLayerMode *layer_mode              = (gpointer) operation;
+  gfloat                 *in                      = in_p;
+  gfloat                 *out                     = out_p;
+  gfloat                 *layer                   = layer_p;
+  gfloat                 *mask                    = mask_p;
+  gfloat                  opacity                 = layer_mode->opacity;
+  GimpLayerColorSpace     blend_space             = layer_mode->blend_space;
+  GimpLayerColorSpace     composite_space         = layer_mode->composite_space;
+  GimpLayerCompositeMode  composite_mode          = layer_mode->real_composite_mode;
+  GimpLayerModeBlendFunc  blend_function          = layer_mode->blend_function;
+  gboolean                composite_needs_in_color;
+  gfloat                 *blend_in;
+  gfloat                 *blend_layer;
+  gfloat                 *blend_out;
+  const Babl             *composite_to_blend_fish = NULL;
+  const Babl             *blend_to_composite_fish = NULL;
+
+  /* make sure we don't process more than GIMP_COMPOSITE_BLEND_MAX_SAMPLES
+   * at a time, so that we don't overflow the stack if we allocate buffers
+   * on it.  note that this has to be done with a nested function call,
+   * because alloca'd buffers remain for the duration of the stack frame.
+   */
+  while (samples > GIMP_COMPOSITE_BLEND_MAX_SAMPLES)
+    {
+      gimp_operation_layer_mode_real_process (operation,
+                                              in, layer, mask, out,
+                                              GIMP_COMPOSITE_BLEND_MAX_SAMPLES,
+                                              roi, level);
+
+      in      += 4 * GIMP_COMPOSITE_BLEND_MAX_SAMPLES;
+      layer   += 4 * GIMP_COMPOSITE_BLEND_MAX_SAMPLES;
+      if (mask)
+        mask  +=     GIMP_COMPOSITE_BLEND_MAX_SAMPLES;
+      out     += 4 * GIMP_COMPOSITE_BLEND_MAX_SAMPLES;
+
+      samples -= GIMP_COMPOSITE_BLEND_MAX_SAMPLES;
+    }
+
+  composite_needs_in_color =
+    composite_mode == GIMP_LAYER_COMPOSITE_UNION ||
+    composite_mode == GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP;
+
+  blend_in    = in;
+  blend_layer = layer;
+  blend_out   = out;
+
+  if (blend_space != GIMP_LAYER_COLOR_SPACE_AUTO)
+    {
+      gimp_assert (composite_space >= 1 && composite_space < 4);
+      gimp_assert (blend_space     >= 1 && blend_space     < 4);
+
+      composite_to_blend_fish = gimp_layer_color_space_fish [composite_space - 1]
+                                                            [blend_space     - 1];
+
+      blend_to_composite_fish = gimp_layer_color_space_fish [blend_space     - 1]
+                                                            [composite_space - 1];
+    }
+
+  /* if we need to convert the samples between the composite and blend
+   * spaces...
+   */
+  if (composite_to_blend_fish)
+    {
+      gint i;
+      gint end;
+
+      if (in != out || composite_needs_in_color)
+        {
+          /* don't convert input in-place if we're not doing in-place output,
+           * or if we're going to need the original input for compositing.
+           */
+          blend_in = g_alloca (sizeof (gfloat) * 4 * samples);
+        }
+      blend_layer  = g_alloca (sizeof (gfloat) * 4 * samples);
+
+      if (in == out) /* in-place detected, avoid clobbering since we need to
+                        read 'in' for the compositing stage  */
+        {
+          if (blend_layer != layer)
+            blend_out = blend_layer;
+          else
+            blend_out = g_alloca (sizeof (gfloat) * 4 * samples);
+        }
+
+      /* samples whose the source or destination alpha is zero are not blended,
+       * and therefore do not need to be converted.  while it's generally
+       * desirable to perform conversion and blending in bulk, when we have
+       * more than a certain number of consecutive unblended samples, the cost
+       * of converting them outweighs the cost of splitting the process around
+       * them to avoid the conversion.
+       */
+
+      i   = ALPHA;
+      end = 4 * samples + ALPHA;
+
+      while (TRUE)
+        {
+          gint first;
+          gint last;
+          gint count;
+
+          /* skip any unblended samples.  the color values of `blend_out` for
+           * these samples are unconstrained, in particular, they may be NaN,
+           * but the alpha values should generally be finite, and specifically
+           * 0 when the source alpha is 0.
+           */
+          while (i < end && (in[i] == 0.0f || layer[i] == 0.0f))
+            {
+              blend_out[i] = 0.0f;
+              i += 4;
+            }
+
+          /* stop if there are no more samples */
+          if (i == end)
+            break;
+
+          /* otherwise, keep scanning the samples until we find
+           * GIMP_COMPOSITE_BLEND_SPLIT_THRESHOLD consecutive unblended
+           * samples.
+           */
+
+          first  = i;
+          i     += 4;
+          last   = i;
+
+          while (i < end && i - last < 4 * GIMP_COMPOSITE_BLEND_SPLIT_THRESHOLD)
+            {
+              gboolean blended;
+
+              blended = (in[i] != 0.0f && layer[i] != 0.0f);
+
+              i += 4;
+              if (blended)
+                last = i;
+            }
+
+          /* convert and blend the samples in the range [first, last) */
+
+          count  = (last - first) / 4;
+          first -= ALPHA;
+
+          babl_process (composite_to_blend_fish,
+                        in + first, blend_in + first, count);
+          babl_process (composite_to_blend_fish,
+                        layer + first, blend_layer + first, count);
+
+          blend_function (blend_in + first, blend_layer + first,
+                          blend_out + first, count);
+
+          babl_process (blend_to_composite_fish,
+                        blend_out + first, blend_out + first, count);
+
+          /* make sure the alpha values of `blend_out` are valid for the
+           * trailing unblended samples.
+           */
+          for (; last < i; last += 4)
+            blend_out[last] = 0.0f;
+        }
+    }
+  else
+    {
+      /* if both blending and compositing use the same color space, things are
+       * much simpler.
+       */
+
+      if (in == out) /* in-place detected, avoid clobbering since we need to
+                        read 'in' for the compositing stage  */
+        {
+          blend_out = g_alloca (sizeof (gfloat) * 4 * samples);
+        }
+
+      blend_function (blend_in, blend_layer, blend_out, samples);
+    }
+
+  if (! gimp_layer_mode_is_subtractive (layer_mode->layer_mode))
+    {
+      switch (composite_mode)
+        {
+        case GIMP_LAYER_COMPOSITE_UNION:
+        case GIMP_LAYER_COMPOSITE_AUTO:
+          composite_union (in, layer, blend_out, mask, opacity,
+                           out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+          composite_clip_to_backdrop (in, layer, blend_out, mask, opacity,
+                                      out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+          composite_clip_to_layer (in, layer, blend_out, mask, opacity,
+                                   out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_INTERSECTION:
+          composite_intersection (in, layer, blend_out, mask, opacity,
+                                  out, samples);
+          break;
+        }
+    }
+  else
+    {
+      switch (composite_mode)
+        {
+        case GIMP_LAYER_COMPOSITE_UNION:
+        case GIMP_LAYER_COMPOSITE_AUTO:
+          composite_union_sub (in, layer, blend_out, mask, opacity,
+                               out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+          composite_clip_to_backdrop_sub (in, layer, blend_out, mask, opacity,
+                                          out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+          composite_clip_to_layer_sub (in, layer, blend_out, mask, opacity,
+                                       out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_INTERSECTION:
+          composite_intersection_sub (in, layer, blend_out, mask, opacity,
+                                      out, samples);
+          break;
+        }
+    }
+
+  return TRUE;
+}
+
+static gboolean
+process_last_node (GeglOperation       *operation,
+                   void                *in_p,
+                   void                *layer_p,
+                   void                *mask_p,
+                   void                *out_p,
+                   glong                samples,
+                   const GeglRectangle *roi,
+                   gint                 level)
+{
+  gfloat *out     = out_p;
+  gfloat *layer   = layer_p;
+  gfloat *mask    = mask_p;
+  gfloat  opacity = GIMP_OPERATION_LAYER_MODE (operation)->opacity;
+
+  while (samples--)
+    {
+      memcpy (out, layer, 3 * sizeof (gfloat));
+
+      out[ALPHA] = layer[ALPHA] * opacity;
+      if (mask)
+        out[ALPHA] *= *mask++;
+
+      layer += 4;
+      out   += 4;
+    }
+
+  return TRUE;
+}
+
+
+/*  public functions  */
+
+
+GimpLayerCompositeRegion
+gimp_operation_layer_mode_get_affected_region (GimpOperationLayerMode *layer_mode)
+{
+  GimpOperationLayerModeClass *klass;
+
+  g_return_val_if_fail (GIMP_IS_OPERATION_LAYER_MODE (layer_mode),
+                        GIMP_LAYER_COMPOSITE_REGION_INTERSECTION);
+
+  klass = GIMP_OPERATION_LAYER_MODE_GET_CLASS (layer_mode);
+
+  if (klass->get_affected_region)
+    return klass->get_affected_region (layer_mode);
+
+  return GIMP_LAYER_COMPOSITE_REGION_INTERSECTION;
+}

app/operations/layer-modes/gimpoperationlayermode.h

@@ -0,0 +1,81 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationlayermode.h
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_LAYER_MODE_H__
+#define __GIMP_OPERATION_LAYER_MODE_H__
+
+
+#include <gegl-plugin.h>
+
+
+#define GIMP_TYPE_OPERATION_LAYER_MODE            (gimp_operation_layer_mode_get_type ())
+#define GIMP_OPERATION_LAYER_MODE(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_OPERATION_LAYER_MODE, GimpOperationLayerMode))
+#define GIMP_OPERATION_LAYER_MODE_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  GIMP_TYPE_OPERATION_LAYER_MODE, GimpOperationLayerModeClass))
+#define GIMP_IS_OPERATION_LAYER_MODE(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_OPERATION_LAYER_MODE))
+#define GIMP_IS_OPERATION_LAYER_MODE_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  GIMP_TYPE_OPERATION_LAYER_MODE))
+#define GIMP_OPERATION_LAYER_MODE_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  GIMP_TYPE_OPERATION_LAYER_MODE, GimpOperationLayerModeClass))
+
+
+typedef struct _GimpOperationLayerModeClass GimpOperationLayerModeClass;
+
+struct _GimpOperationLayerMode
+{
+  GeglOperationPointComposer3  parent_instance;
+
+  GimpLayerMode                layer_mode;
+  gdouble                      opacity;
+  GimpLayerColorSpace          blend_space;
+  GimpLayerColorSpace          composite_space;
+  GimpLayerCompositeMode       composite_mode;
+
+  GimpLayerCompositeMode       real_composite_mode;
+  GimpLayerModeFunc            function;
+  GimpLayerModeBlendFunc       blend_function;
+  gboolean                     is_last_node;
+};
+
+struct _GimpOperationLayerModeClass
+{
+  GeglOperationPointComposer3Class  parent_class;
+
+  /*  virtual functions  */
+  gboolean                 (* process)             (GeglOperation          *operation,
+                                                    void                   *in,
+                                                    void                   *aux,
+                                                    void                   *mask,
+                                                    void                   *out,
+                                                    glong                   samples,
+                                                    const GeglRectangle    *roi,
+                                                    gint                    level);
+
+  /* Returns the composite region (any combination of the layer and the
+   * backdrop) that the layer mode affects.  Most modes only affect the
+   * overlapping region, and don't need to override this function.
+   */
+  GimpLayerCompositeRegion (* get_affected_region) (GimpOperationLayerMode *layer_mode);
+};
+
+
+GType                    gimp_operation_layer_mode_get_type            (void) G_GNUC_CONST;
+
+GimpLayerCompositeRegion gimp_operation_layer_mode_get_affected_region (GimpOperationLayerMode *layer_mode);
+
+
+#endif /* __GIMP_OPERATION_LAYER_MODE_H__ */

app/operations/layer-modes/gimpoperationmerge.c

@@ -0,0 +1,243 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationmerge.c
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *               2017 Ell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+
+#include "../operations-types.h"
+
+#include "gimpoperationmerge.h"
+
+
+static gboolean   gimp_operation_merge_process (GeglOperation       *op,
+                                                void                *in,
+                                                void                *layer,
+                                                void                *mask,
+                                                void                *out,
+                                                glong                samples,
+                                                const GeglRectangle *roi,
+                                                gint                 level);
+
+
+G_DEFINE_TYPE (GimpOperationMerge, gimp_operation_merge,
+               GIMP_TYPE_OPERATION_LAYER_MODE)
+
+
+static void
+gimp_operation_merge_class_init (GimpOperationMergeClass *klass)
+{
+  GeglOperationClass          *operation_class  = GEGL_OPERATION_CLASS (klass);
+  GimpOperationLayerModeClass *layer_mode_class = GIMP_OPERATION_LAYER_MODE_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name",        "gimp:merge",
+                                 "description", "GIMP merge mode operation",
+                                 NULL);
+
+  layer_mode_class->process = gimp_operation_merge_process;
+}
+
+static void
+gimp_operation_merge_init (GimpOperationMerge *self)
+{
+}
+
+static gboolean
+gimp_operation_merge_process (GeglOperation       *op,
+                              void                *in_p,
+                              void                *layer_p,
+                              void                *mask_p,
+                              void                *out_p,
+                              glong                samples,
+                              const GeglRectangle *roi,
+                              gint                 level)
+{
+  GimpOperationLayerMode *layer_mode = (gpointer) op;
+  gfloat                 *in         = in_p;
+  gfloat                 *out        = out_p;
+  gfloat                 *layer      = layer_p;
+  gfloat                 *mask       = mask_p;
+  gfloat                  opacity    = layer_mode->opacity;
+  const gboolean          has_mask   = mask != NULL;
+
+  switch (layer_mode->real_composite_mode)
+    {
+    case GIMP_LAYER_COMPOSITE_UNION:
+    case GIMP_LAYER_COMPOSITE_AUTO:
+      while (samples--)
+        {
+          gfloat in_alpha    = in[ALPHA];
+          gfloat layer_alpha = layer[ALPHA] * opacity;
+          gfloat new_alpha;
+          gint   b;
+
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          in_alpha = MIN (in_alpha, 1.0f - layer_alpha);
+          new_alpha  = in_alpha + layer_alpha;
+
+          if (new_alpha)
+            {
+              gfloat ratio = layer_alpha / new_alpha;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b] + (layer[b] - in[b]) * ratio;
+                }
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+      while (samples--)
+        {
+          gfloat in_alpha    = in[ALPHA];
+          gfloat layer_alpha = layer[ALPHA] * opacity;
+          gint   b;
+
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          layer_alpha -= 1.0f - in_alpha;
+
+          if (layer_alpha > 0.0f)
+            {
+              gfloat ratio = layer_alpha / in_alpha;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b] + (layer[b] - in[b]) * ratio;
+                }
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+
+          out[ALPHA] = in_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+      while (samples--)
+        {
+          gfloat layer_alpha = layer[ALPHA] * opacity;
+          gint   b;
+
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          if (layer_alpha != 0.0f)
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b];
+                }
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+
+          out[ALPHA] = layer_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_INTERSECTION:
+      while (samples--)
+        {
+          gfloat in_alpha    = in[ALPHA];
+          gfloat layer_alpha = layer[ALPHA] * opacity;
+          gint   b;
+
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          layer_alpha -= 1.0f - in_alpha;
+          layer_alpha = MAX (layer_alpha, 0.0f);
+
+          if (layer_alpha != 0.0f)
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b];
+                }
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+
+          out[ALPHA] = layer_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+    }
+
+  return TRUE;
+}

app/operations/layer-modes/gimpoperationmerge.h

@@ -0,0 +1,54 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationmerge.h
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *               2017 Ell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_MERGE_H__
+#define __GIMP_OPERATION_MERGE_H__
+
+
+#include "gimpoperationlayermode.h"
+
+
+#define GIMP_TYPE_OPERATION_MERGE            (gimp_operation_merge_get_type ())
+#define GIMP_OPERATION_MERGE(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_OPERATION_MERGE, GimpOperationMerge))
+#define GIMP_OPERATION_MERGE_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  GIMP_TYPE_OPERATION_MERGE, GimpOperationMergeClass))
+#define GIMP_IS_OPERATION_MERGE(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_OPERATION_MERGE))
+#define GIMP_IS_OPERATION_MERGE_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  GIMP_TYPE_OPERATION_MERGE))
+#define GIMP_OPERATION_MERGE_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  GIMP_TYPE_OPERATION_MERGE, GimpOperationMergeClass))
+
+
+typedef struct _GimpOperationMerge      GimpOperationMerge;
+typedef struct _GimpOperationMergeClass GimpOperationMergeClass;
+
+struct _GimpOperationMerge
+{
+  GimpOperationLayerMode  parent_instance;
+};
+
+struct _GimpOperationMergeClass
+{
+  GimpOperationLayerModeClass  parent_class;
+};
+
+
+GType   gimp_operation_merge_get_type (void) G_GNUC_CONST;
+
+
+#endif /* __GIMP_OPERATION_MERGE_H__ */

app/operations/layer-modes/gimpoperationnormal-sse2.c

@@ -0,0 +1,264 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationnormal-sse2.c
+ * Copyright (C) 2013 Daniel Sabo
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+
+#include "operations/operations-types.h"
+
+#include "gimpoperationnormal.h"
+
+
+#if COMPILE_SSE2_INTRINISICS
+
+/* SSE2 */
+#include <emmintrin.h>
+
+
+gboolean
+gimp_operation_normal_process_sse2 (GeglOperation       *op,
+                                    void                *in_p,
+                                    void                *layer_p,
+                                    void                *mask_p,
+                                    void                *out_p,
+                                    glong                samples,
+                                    const GeglRectangle *roi,
+                                    gint                 level)
+{
+  /* check alignment */
+  if ((((uintptr_t)in_p) | ((uintptr_t)layer_p) | ((uintptr_t)out_p)) & 0x0F)
+    {
+      return gimp_operation_normal_process (op,
+                                            in_p, layer_p, mask_p, out_p,
+                                            samples, roi, level);
+    }
+  else
+    {
+      GimpOperationLayerMode *layer_mode      = (gpointer) op;
+      gfloat                  opacity         = layer_mode->opacity;
+      gfloat                 *mask            = mask_p;
+      const                   __v4sf *v_in    = (const __v4sf*) in_p;
+      const                   __v4sf *v_layer = (const __v4sf*) layer_p;
+                              __v4sf *v_out   = (      __v4sf*) out_p;
+
+      const __v4sf one       = _mm_set1_ps (1.0f);
+      const __v4sf v_opacity = _mm_set1_ps (opacity);
+
+      switch (layer_mode->real_composite_mode)
+        {
+        case GIMP_LAYER_COMPOSITE_UNION:
+        case GIMP_LAYER_COMPOSITE_AUTO:
+          while (samples--)
+            {
+              __v4sf rgba_in, rgba_layer, alpha;
+
+              rgba_in    = *v_in++;
+              rgba_layer = *v_layer++;
+
+              /* expand alpha */
+              alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_layer,
+                                                 _MM_SHUFFLE (3, 3, 3, 3));
+
+              if (mask)
+                {
+                  __v4sf mask_alpha;
+
+                  /* multiply layer's alpha by the mask */
+                  mask_alpha = _mm_set1_ps (*mask++);
+                  alpha = alpha * mask_alpha;
+                }
+
+              alpha = alpha * v_opacity;
+
+              if (_mm_ucomigt_ss (alpha, _mm_setzero_ps ()))
+                {
+                  __v4sf dst_alpha, a_term, out_pixel, out_alpha, out_pixel_rbaa;
+
+                  /* expand alpha */
+                  dst_alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_in,
+                                                         _MM_SHUFFLE (3, 3, 3, 3));
+
+                  /* a_term = dst_a * (1.0 - src_a) */
+                  a_term = dst_alpha * (one - alpha);
+
+                  /* out(color) = src * src_a + dst * a_term */
+                  out_pixel = rgba_layer * alpha + rgba_in * a_term;
+
+                  /* out(alpha) = 1.0 * src_a + 1.0 * a_term */
+                  out_alpha = alpha + a_term;
+
+                  /* un-premultiply */
+                  out_pixel = out_pixel / out_alpha;
+
+                  /* swap in the real alpha */
+                  out_pixel_rbaa = _mm_shuffle_ps (out_pixel, out_alpha, _MM_SHUFFLE (3, 3, 2, 0));
+                  out_pixel = _mm_shuffle_ps (out_pixel, out_pixel_rbaa, _MM_SHUFFLE (2, 1, 1, 0));
+
+                  *v_out++ = out_pixel;
+                }
+              else
+                {
+                  *v_out++ = rgba_in;
+                }
+            }
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+          while (samples--)
+            {
+              __v4sf rgba_in, rgba_layer, alpha;
+
+              rgba_in    = *v_in++;
+              rgba_layer = *v_layer++;
+
+              /* expand alpha */
+              alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_layer,
+                                                 _MM_SHUFFLE (3, 3, 3, 3));
+
+              if (mask)
+                {
+                  __v4sf mask_alpha;
+
+                  /* multiply layer's alpha by the mask */
+                  mask_alpha = _mm_set1_ps (*mask++);
+                  alpha = alpha * mask_alpha;
+                }
+
+              alpha = alpha * v_opacity;
+
+              if (_mm_ucomigt_ss (alpha, _mm_setzero_ps ()))
+                {
+                  __v4sf dst_alpha, out_pixel, out_pixel_rbaa;
+
+                  /* expand alpha */
+                  dst_alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_in,
+                                                         _MM_SHUFFLE (3, 3, 3, 3));
+
+                  /* out(color) = dst * (1 - src_a) + src * src_a */
+                  out_pixel = rgba_in + (rgba_layer - rgba_in) * alpha;
+
+                  /* swap in the real alpha */
+                  out_pixel_rbaa = _mm_shuffle_ps (out_pixel, dst_alpha, _MM_SHUFFLE (3, 3, 2, 0));
+                  out_pixel = _mm_shuffle_ps (out_pixel, out_pixel_rbaa, _MM_SHUFFLE (2, 1, 1, 0));
+
+                  *v_out++ = out_pixel;
+                }
+              else
+                {
+                  *v_out++ = rgba_in;
+                }
+            }
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+          while (samples--)
+            {
+              __v4sf rgba_in, rgba_layer, alpha;
+              __v4sf out_pixel, out_pixel_rbaa;
+
+              rgba_in    = *v_in++;
+              rgba_layer = *v_layer++;
+
+              /* expand alpha */
+              alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_layer,
+                                                 _MM_SHUFFLE (3, 3, 3, 3));
+
+              if (mask)
+                {
+                  __v4sf mask_alpha;
+
+                  /* multiply layer's alpha by the mask */
+                  mask_alpha = _mm_set1_ps (*mask++);
+                  alpha = alpha * mask_alpha;
+                }
+
+              alpha = alpha * v_opacity;
+
+              if (_mm_ucomigt_ss (alpha, _mm_setzero_ps ()))
+                {
+                  /* out(color) = src */
+                  out_pixel = rgba_layer;
+                }
+              else
+                {
+                  out_pixel = rgba_in;
+                }
+
+              /* swap in the real alpha */
+              out_pixel_rbaa = _mm_shuffle_ps (out_pixel, alpha, _MM_SHUFFLE (3, 3, 2, 0));
+              out_pixel = _mm_shuffle_ps (out_pixel, out_pixel_rbaa, _MM_SHUFFLE (2, 1, 1, 0));
+
+              *v_out++ = out_pixel;
+            }
+          break;
+
+        case GIMP_LAYER_COMPOSITE_INTERSECTION:
+          while (samples--)
+            {
+              __v4sf rgba_in, rgba_layer, alpha;
+              __v4sf out_pixel, out_pixel_rbaa;
+
+              rgba_in    = *v_in++;
+              rgba_layer = *v_layer++;
+
+              /* expand alpha */
+              alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_layer,
+                                                 _MM_SHUFFLE (3, 3, 3, 3));
+
+              if (mask)
+                {
+                  __v4sf mask_alpha;
+
+                  /* multiply layer's alpha by the mask */
+                  mask_alpha = _mm_set1_ps (*mask++);
+                  alpha = alpha * mask_alpha;
+                }
+
+              alpha = alpha * v_opacity;
+
+              /* multiply the alpha by in's alpha */
+              alpha *= (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_in,
+                                                  _MM_SHUFFLE (3, 3, 3, 3));
+
+              if (_mm_ucomigt_ss (alpha, _mm_setzero_ps ()))
+                {
+                  /* out(color) = src */
+                  out_pixel = rgba_layer;
+                }
+              else
+                {
+                  out_pixel = rgba_in;
+                }
+
+              /* swap in the real alpha */
+              out_pixel_rbaa = _mm_shuffle_ps (out_pixel, alpha, _MM_SHUFFLE (3, 3, 2, 0));
+              out_pixel = _mm_shuffle_ps (out_pixel, out_pixel_rbaa, _MM_SHUFFLE (2, 1, 1, 0));
+
+              *v_out++ = out_pixel;
+            }
+          break;
+        }
+    }
+
+  return TRUE;
+}
+
+#endif /* COMPILE_SSE2_INTRINISICS */

app/operations/layer-modes/gimpoperationnormal-sse4.c

@@ -0,0 +1,260 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationnormalmode-sse2.c
+ * Copyright (C) 2013 Daniel Sabo
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+
+#include "operations/operations-types.h"
+
+#include "gimpoperationnormal.h"
+
+
+#if COMPILE_SSE4_1_INTRINISICS
+
+/* SSE4 */
+#include <smmintrin.h>
+
+
+gboolean
+gimp_operation_normal_process_sse4 (GeglOperation       *op,
+                                    void                *in_p,
+                                    void                *layer_p,
+                                    void                *mask_p,
+                                    void                *out_p,
+                                    glong                samples,
+                                    const GeglRectangle *roi,
+                                    gint                 level)
+{
+  /* check alignment */
+  if ((((uintptr_t)in_p) | ((uintptr_t)layer_p) | ((uintptr_t)out_p)) & 0x0F)
+    {
+      return gimp_operation_normal_process (op,
+                                            in_p, layer_p, mask_p, out_p,
+                                            samples, roi, level);
+    }
+  else
+    {
+      GimpOperationLayerMode *layer_mode      = (gpointer) op;
+      gfloat                  opacity         = layer_mode->opacity;
+      gfloat                 *mask            = mask_p;
+      const                   __v4sf *v_in    = (const __v4sf*) in_p;
+      const                   __v4sf *v_layer = (const __v4sf*) layer_p;
+                              __v4sf *v_out   = (      __v4sf*) out_p;
+
+      const __v4sf one       = _mm_set1_ps (1.0f);
+      const __v4sf v_opacity = _mm_set1_ps (opacity);
+
+      switch (layer_mode->real_composite_mode)
+        {
+        case GIMP_LAYER_COMPOSITE_UNION:
+        case GIMP_LAYER_COMPOSITE_AUTO:
+          while (samples--)
+            {
+              __v4sf rgba_in, rgba_layer, alpha;
+
+              rgba_in    = *v_in++;
+              rgba_layer = *v_layer++;
+
+              /* expand alpha */
+              alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_layer,
+                                                 _MM_SHUFFLE (3, 3, 3, 3));
+
+              if (mask)
+                {
+                  __v4sf mask_alpha;
+
+                  /* multiply layer's alpha by the mask */
+                  mask_alpha = _mm_set1_ps (*mask++);
+                  alpha = alpha * mask_alpha;
+                }
+
+              alpha = alpha * v_opacity;
+
+              if (_mm_ucomigt_ss (alpha, _mm_setzero_ps ()))
+                {
+                  __v4sf dst_alpha, a_term, out_pixel, out_alpha;
+
+                  /* expand alpha */
+                  dst_alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_in,
+                                                         _MM_SHUFFLE (3, 3, 3, 3));
+
+                  /* a_term = dst_a * (1.0 - src_a) */
+                  a_term = dst_alpha * (one - alpha);
+
+                  /* out(color) = src * src_a + dst * a_term */
+                  out_pixel = rgba_layer * alpha + rgba_in * a_term;
+
+                  /* out(alpha) = 1.0 * src_a + 1.0 * a_term */
+                  out_alpha = alpha + a_term;
+
+                  /* un-premultiply */
+                  out_pixel = out_pixel / out_alpha;
+
+                  /* swap in the real alpha */
+                  out_pixel = _mm_blend_ps (out_pixel, out_alpha, 0x08);
+
+                  *v_out++ = out_pixel;
+                }
+              else
+                {
+                  *v_out++ = rgba_in;
+                }
+            }
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+          while (samples--)
+            {
+              __v4sf rgba_in, rgba_layer, alpha;
+
+              rgba_in    = *v_in++;
+              rgba_layer = *v_layer++;
+
+              /* expand alpha */
+              alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_layer,
+                                                 _MM_SHUFFLE (3, 3, 3, 3));
+
+              if (mask)
+                {
+                  __v4sf mask_alpha;
+
+                  /* multiply layer's alpha by the mask */
+                  mask_alpha = _mm_set1_ps (*mask++);
+                  alpha = alpha * mask_alpha;
+                }
+
+              alpha = alpha * v_opacity;
+
+              if (_mm_ucomigt_ss (alpha, _mm_setzero_ps ()))
+                {
+                  __v4sf dst_alpha, out_pixel;
+
+                  /* expand alpha */
+                  dst_alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_in,
+                                                         _MM_SHUFFLE (3, 3, 3, 3));
+
+                  /* out(color) = dst * (1 - src_a) + src * src_a */
+                  out_pixel = rgba_in + (rgba_layer - rgba_in) * alpha;
+
+                  /* swap in the real alpha */
+                  out_pixel = _mm_blend_ps (out_pixel, dst_alpha, 0x08);
+
+                  *v_out++ = out_pixel;
+                }
+              else
+                {
+                  *v_out++ = rgba_in;
+                }
+            }
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+          while (samples--)
+            {
+              __v4sf rgba_in, rgba_layer, alpha;
+              __v4sf out_pixel;
+
+              rgba_in    = *v_in++;
+              rgba_layer = *v_layer++;
+
+              /* expand alpha */
+              alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_layer,
+                                                 _MM_SHUFFLE (3, 3, 3, 3));
+
+              if (mask)
+                {
+                  __v4sf mask_alpha;
+
+                  /* multiply layer's alpha by the mask */
+                  mask_alpha = _mm_set1_ps (*mask++);
+                  alpha = alpha * mask_alpha;
+                }
+
+              alpha = alpha * v_opacity;
+
+              if (_mm_ucomigt_ss (alpha, _mm_setzero_ps ()))
+                {
+                  /* out(color) = src */
+                  out_pixel = rgba_layer;
+                }
+              else
+                {
+                  out_pixel = rgba_in;
+                }
+
+              /* swap in the real alpha */
+              out_pixel = _mm_blend_ps (out_pixel, alpha, 0x08);
+
+              *v_out++ = out_pixel;
+            }
+          break;
+
+        case GIMP_LAYER_COMPOSITE_INTERSECTION:
+          while (samples--)
+            {
+              __v4sf rgba_in, rgba_layer, alpha;
+              __v4sf out_pixel;
+
+              rgba_in    = *v_in++;
+              rgba_layer = *v_layer++;
+
+              /* expand alpha */
+              alpha = (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_layer,
+                                                 _MM_SHUFFLE (3, 3, 3, 3));
+
+              if (mask)
+                {
+                  __v4sf mask_alpha;
+
+                  /* multiply layer's alpha by the mask */
+                  mask_alpha = _mm_set1_ps (*mask++);
+                  alpha = alpha * mask_alpha;
+                }
+
+              alpha = alpha * v_opacity;
+
+              /* multiply the alpha by in's alpha */
+              alpha *= (__v4sf)_mm_shuffle_epi32 ((__m128i)rgba_in,
+                                                  _MM_SHUFFLE (3, 3, 3, 3));
+
+              if (_mm_ucomigt_ss (alpha, _mm_setzero_ps ()))
+                {
+                  /* out(color) = src */
+                  out_pixel = rgba_layer;
+                }
+              else
+                {
+                  out_pixel = rgba_in;
+                }
+
+              /* swap in the real alpha */
+              out_pixel = _mm_blend_ps (out_pixel, alpha, 0x08);
+
+              *v_out++ = out_pixel;
+            }
+          break;
+        }
+    }
+
+  return TRUE;
+}
+
+#endif /* COMPILE_SSE4_1_INTRINISICS */

app/operations/layer-modes/gimpoperationnormal.c

@@ -0,0 +1,266 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationnormalmode.c
+ * Copyright (C) 2012 Michael Natterer <mitch@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gio/gio.h>
+#include <gegl-plugin.h>
+
+#include "libgimpbase/gimpbase.h"
+
+#include "../operations-types.h"
+
+#include "gimpoperationnormal.h"
+
+
+G_DEFINE_TYPE (GimpOperationNormal, gimp_operation_normal,
+               GIMP_TYPE_OPERATION_LAYER_MODE)
+
+
+static const gchar* reference_xml = "<?xml version='1.0' encoding='UTF-8'?>"
+"<gegl>"
+"<node operation='gimp:normal'>"
+"  <node operation='gegl:load'>"
+"    <params>"
+"      <param name='path'>blending-test-B.png</param>"
+"    </params>"
+"  </node>"
+"</node>"
+"<node operation='gegl:load'>"
+"  <params>"
+"    <param name='path'>blending-test-A.png</param>"
+"  </params>"
+"</node>"
+"</gegl>";
+
+
+static void
+gimp_operation_normal_class_init (GimpOperationNormalClass *klass)
+{
+  GeglOperationClass          *operation_class  = GEGL_OPERATION_CLASS (klass);
+  GimpOperationLayerModeClass *layer_mode_class = GIMP_OPERATION_LAYER_MODE_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name",                  "gimp:normal",
+                                 "description",           "GIMP normal mode operation",
+                                 "reference-image",       "normal-mode.png",
+                                 "reference-composition", reference_xml,
+                                 NULL);
+
+  layer_mode_class->process = gimp_operation_normal_process;
+
+#if COMPILE_SSE2_INTRINISICS
+  if (gimp_cpu_accel_get_support() & GIMP_CPU_ACCEL_X86_SSE2)
+    layer_mode_class->process = gimp_operation_normal_process_sse2;
+#endif /* COMPILE_SSE2_INTRINISICS */
+
+#if COMPILE_SSE4_1_INTRINISICS
+  if (gimp_cpu_accel_get_support() & GIMP_CPU_ACCEL_X86_SSE4_1)
+    layer_mode_class->process = gimp_operation_normal_process_sse4;
+#endif /* COMPILE_SSE4_1_INTRINISICS */
+}
+
+static void
+gimp_operation_normal_init (GimpOperationNormal *self)
+{
+}
+
+gboolean
+gimp_operation_normal_process (GeglOperation       *op,
+                               void                *in_p,
+                               void                *layer_p,
+                               void                *mask_p,
+                               void                *out_p,
+                               glong                samples,
+                               const GeglRectangle *roi,
+                               gint                 level)
+{
+  GimpOperationLayerMode *layer_mode = (gpointer) op;
+  gfloat                 *in         = in_p;
+  gfloat                 *out        = out_p;
+  gfloat                 *layer      = layer_p;
+  gfloat                 *mask       = mask_p;
+  gfloat                  opacity    = layer_mode->opacity;
+  const gboolean          has_mask   = mask != NULL;
+
+  switch (layer_mode->real_composite_mode)
+    {
+    case GIMP_LAYER_COMPOSITE_UNION:
+    case GIMP_LAYER_COMPOSITE_AUTO:
+      while (samples--)
+        {
+          gfloat layer_alpha;
+
+          layer_alpha = layer[ALPHA] * opacity;
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          out[ALPHA] = layer_alpha + in[ALPHA] - layer_alpha * in[ALPHA];
+
+          if (out[ALPHA])
+            {
+              gfloat layer_weight = layer_alpha / out[ALPHA];
+              gfloat in_weight    = 1.0f - layer_weight;
+              gint   b;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b] * layer_weight + in[b] * in_weight;
+                }
+            }
+          else
+            {
+              gint b;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+      while (samples--)
+        {
+          gfloat layer_alpha;
+
+          layer_alpha = layer[ALPHA] * opacity;
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          out[ALPHA] = in[ALPHA];
+
+          if (out[ALPHA])
+            {
+              gint b;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b] + (layer[b] - in[b]) * layer_alpha;
+                }
+            }
+          else
+            {
+              gint b;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+      while (samples--)
+        {
+          gfloat layer_alpha;
+
+          layer_alpha = layer[ALPHA] * opacity;
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          out[ALPHA] = layer_alpha;
+
+          if (out[ALPHA])
+            {
+              gint b;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b];
+                }
+            }
+          else
+            {
+              gint b;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_INTERSECTION:
+      while (samples--)
+        {
+          gfloat layer_alpha;
+
+          layer_alpha = layer[ALPHA] * opacity;
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          out[ALPHA] = in[ALPHA] * layer_alpha;
+
+          if (out[ALPHA])
+            {
+              gint b;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b];
+                }
+            }
+          else
+            {
+              gint b;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+    }
+
+  return TRUE;
+}

app/operations/layer-modes/gimpoperationnormal.h

@@ -0,0 +1,91 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationnormal.h
+ * Copyright (C) 2012 Michael Natterer <mitch@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_NORMAL_H__
+#define __GIMP_OPERATION_NORMAL_H__
+
+
+#include "gimpoperationlayermode.h"
+
+
+#define GIMP_TYPE_OPERATION_NORMAL            (gimp_operation_normal_get_type ())
+#define GIMP_OPERATION_NORMAL(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_OPERATION_NORMAL, GimpOperationNormal))
+#define GIMP_OPERATION_NORMAL_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  GIMP_TYPE_OPERATION_NORMAL, GimpOperationNormalClass))
+#define GIMP_IS_OPERATION_NORMAL(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_OPERATION_NORMAL))
+#define GIMP_IS_OPERATION_NORMAL_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  GIMP_TYPE_OPERATION_NORMAL))
+#define GIMP_OPERATION_NORMAL_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  GIMP_TYPE_OPERATION_NORMAL, GimpOperationNormalClass))
+
+
+typedef struct _GimpOperationNormal      GimpOperationNormal;
+typedef struct _GimpOperationNormalClass GimpOperationNormalClass;
+
+struct _GimpOperationNormal
+{
+  GimpOperationLayerMode  parent_instance;
+};
+
+struct _GimpOperationNormalClass
+{
+  GimpOperationLayerModeClass  parent_class;
+};
+
+
+GType      gimp_operation_normal_get_type     (void) G_GNUC_CONST;
+
+
+/*  protected  */
+
+gboolean   gimp_operation_normal_process      (GeglOperation       *op,
+                                               void                *in,
+                                               void                *layer,
+                                               void                *mask,
+                                               void                *out,
+                                               glong                samples,
+                                               const GeglRectangle *roi,
+                                               gint                 level);
+
+#if COMPILE_SSE2_INTRINISICS
+
+gboolean   gimp_operation_normal_process_sse2 (GeglOperation       *op,
+                                               void                *in,
+                                               void                *layer,
+                                               void                *mask,
+                                               void                *out,
+                                               glong                samples,
+                                               const GeglRectangle *roi,
+                                               gint                 level);
+
+#endif /* COMPILE_SSE2_INTRINISICS */
+
+#if COMPILE_SSE4_1_INTRINISICS
+
+gboolean   gimp_operation_normal_process_sse4 (GeglOperation       *op,
+                                               void                *in,
+                                               void                *layer,
+                                               void                *mask,
+                                               void                *out,
+                                               glong                samples,
+                                               const GeglRectangle *roi,
+                                               gint                 level);
+
+#endif /* COMPILE_SSE4_1_INTRINISICS */
+
+
+#endif /* __GIMP_OPERATION_NORMAL_H__ */

app/operations/layer-modes/gimpoperationpassthrough.c

@@ -0,0 +1,106 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationpassthrough.c
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *               2017 Ell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+
+#include "../operations-types.h"
+
+#include "gimp-layer-modes.h"
+#include "gimpoperationpassthrough.h"
+
+
+static gboolean   gimp_operation_pass_through_parent_process (GeglOperation        *operation,
+                                                              GeglOperationContext *context,
+                                                              const gchar          *output_prop,
+                                                              const GeglRectangle  *result,
+                                                              gint                  level);
+
+
+G_DEFINE_TYPE (GimpOperationPassThrough, gimp_operation_pass_through,
+               GIMP_TYPE_OPERATION_REPLACE)
+
+#define parent_class gimp_operation_pass_through_parent_class
+
+
+static void
+gimp_operation_pass_through_class_init (GimpOperationPassThroughClass *klass)
+{
+  GeglOperationClass          *operation_class  = GEGL_OPERATION_CLASS (klass);
+  GimpOperationLayerModeClass *layer_mode_class = GIMP_OPERATION_LAYER_MODE_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name",        "gimp:pass-through",
+                                 "description", "GIMP pass through mode operation",
+                                 NULL);
+
+  operation_class->process              = gimp_operation_pass_through_parent_process;
+
+  /* don't use REPLACE mode's specialized get_affected_region(); PASS_THROUGH
+   * behaves like an ordinary layer mode here.
+   */
+  layer_mode_class->get_affected_region = NULL;
+}
+
+static void
+gimp_operation_pass_through_init (GimpOperationPassThrough *self)
+{
+}
+
+static gboolean
+gimp_operation_pass_through_parent_process (GeglOperation        *operation,
+                                            GeglOperationContext *context,
+                                            const gchar          *output_prop,
+                                            const GeglRectangle  *result,
+                                            gint                  level)
+{
+  GimpOperationLayerMode *layer_mode = (gpointer) operation;
+
+  /* if the layer's opacity is 100%, it has no mask, and its composite mode
+   * contains "aux" (the latter should always be the case for pass through
+   * mode,) we can just pass "aux" directly as output.  note that the same
+   * optimization would more generally apply to REPLACE mode, save for the fact
+   * that when both the backdrop and the layer have a pixel with 0% alpha, we
+   * want to maintain the color value of the backdrop, not the layer; since,
+   * for pass through groups, the layer is already composited against the
+   * backdrop, such pixels will have the same color value for both the backdrop
+   * and the layer.
+   */
+  if (layer_mode->opacity == 1.0                            &&
+      ! gegl_operation_context_get_object (context, "aux2") &&
+      (gimp_layer_mode_get_included_region (layer_mode->layer_mode,
+                                            layer_mode->real_composite_mode) &
+       GIMP_LAYER_COMPOSITE_REGION_SOURCE))
+    {
+      GObject *aux;
+
+      aux = gegl_operation_context_get_object (context, "aux");
+
+      gegl_operation_context_set_object (context, "output", aux);
+
+      return TRUE;
+    }
+
+  return GEGL_OPERATION_CLASS (parent_class)->process (operation, context,
+                                                       output_prop, result,
+                                                       level);
+}

app/operations/layer-modes/gimpoperationpassthrough.h

@@ -0,0 +1,54 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationpassthrough.h
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *               2017 Ell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_PASS_THROUGH_H__
+#define __GIMP_OPERATION_PASS_THROUGH_H__
+
+
+#include "gimpoperationreplace.h"
+
+
+#define GIMP_TYPE_OPERATION_PASS_THROUGH            (gimp_operation_pass_through_get_type ())
+#define GIMP_OPERATION_PASS_THROUGH(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_OPERATION_PASS_THROUGH, GimpOperationPassThrough))
+#define GIMP_OPERATION_PASS_THROUGH_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  GIMP_TYPE_OPERATION_PASS_THROUGH, GimpOperationPassThroughClass))
+#define GIMP_IS_OPERATION_PASS_THROUGH(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_OPERATION_PASS_THROUGH))
+#define GIMP_IS_OPERATION_PASS_THROUGH_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  GIMP_TYPE_OPERATION_PASS_THROUGH))
+#define GIMP_OPERATION_PASS_THROUGH_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  GIMP_TYPE_OPERATION_PASS_THROUGH, GimpOperationPassThroughClass))
+
+
+typedef struct _GimpOperationPassThrough      GimpOperationPassThrough;
+typedef struct _GimpOperationPassThroughClass GimpOperationPassThroughClass;
+
+struct _GimpOperationPassThrough
+{
+  GimpOperationReplace parent_instance;
+};
+
+struct _GimpOperationPassThroughClass
+{
+  GimpOperationReplaceClass parent_class;
+};
+
+
+GType   gimp_operation_pass_through_get_type (void) G_GNUC_CONST;
+
+
+#endif /* __GIMP_OPERATION_PASS_THROUGH_H__ */

app/operations/layer-modes/gimpoperationreplace.c

@@ -0,0 +1,213 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationreplace.c
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+
+#include "../operations-types.h"
+
+#include "gimpoperationreplace.h"
+
+
+static gboolean                   gimp_operation_replace_process             (GeglOperation          *op,
+                                                                              void                   *in,
+                                                                              void                   *layer,
+                                                                              void                   *mask,
+                                                                              void                   *out,
+                                                                              glong                   samples,
+                                                                              const GeglRectangle    *roi,
+                                                                              gint                    level);
+static GimpLayerCompositeRegion   gimp_operation_replace_get_affected_region (GimpOperationLayerMode *layer_mode);
+
+
+G_DEFINE_TYPE (GimpOperationReplace, gimp_operation_replace,
+               GIMP_TYPE_OPERATION_LAYER_MODE)
+
+
+static void
+gimp_operation_replace_class_init (GimpOperationReplaceClass *klass)
+{
+  GeglOperationClass          *operation_class  = GEGL_OPERATION_CLASS (klass);
+  GimpOperationLayerModeClass *layer_mode_class = GIMP_OPERATION_LAYER_MODE_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name",        "gimp:replace",
+                                 "description", "GIMP replace mode operation",
+                                 NULL);
+
+  layer_mode_class->process             = gimp_operation_replace_process;
+  layer_mode_class->get_affected_region = gimp_operation_replace_get_affected_region;
+}
+
+static void
+gimp_operation_replace_init (GimpOperationReplace *self)
+{
+}
+
+static gboolean
+gimp_operation_replace_process (GeglOperation       *op,
+                                void                *in_p,
+                                void                *layer_p,
+                                void                *mask_p,
+                                void                *out_p,
+                                glong                samples,
+                                const GeglRectangle *roi,
+                                gint                 level)
+{
+  GimpOperationLayerMode *layer_mode = (gpointer) op;
+  gfloat                 *in         = in_p;
+  gfloat                 *out        = out_p;
+  gfloat                 *layer      = layer_p;
+  gfloat                 *mask       = mask_p;
+  gfloat                  opacity    = layer_mode->opacity;
+  const gboolean          has_mask   = mask != NULL;
+
+  switch (layer_mode->real_composite_mode)
+    {
+    case GIMP_LAYER_COMPOSITE_UNION:
+    case GIMP_LAYER_COMPOSITE_AUTO:
+      while (samples--)
+        {
+          gfloat opacity_value = opacity;
+          gfloat new_alpha;
+          gint   b;
+
+          if (has_mask)
+            opacity_value *= *mask;
+
+          new_alpha = (layer[ALPHA] - in[ALPHA]) * opacity_value + in[ALPHA];
+
+          if (new_alpha)
+            {
+              gfloat ratio = opacity_value * layer[ALPHA] / new_alpha;
+
+              for (b = RED; b < ALPHA; b++)
+                out[b] = (layer[b] - in[b]) * ratio + in[b];
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                out[b] = in[b];
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+      while (samples--)
+        {
+          gfloat opacity_value = opacity;
+          gfloat new_alpha;
+          gint   b;
+
+          if (has_mask)
+            opacity_value *= *mask;
+
+          new_alpha = in[ALPHA] * (1.0f - opacity_value);
+
+          for (b = RED; b < ALPHA; b++)
+            out[b] = in[b];
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+      while (samples--)
+        {
+          gfloat opacity_value = opacity;
+          gfloat new_alpha;
+          gint   b;
+
+          if (has_mask)
+            opacity_value *= *mask;
+
+          new_alpha = layer[ALPHA] * opacity_value;
+
+          if (new_alpha)
+            {
+              for (b = RED; b < ALPHA; b++)
+                out[b] = layer[b];
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                out[b] = in[b];
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_INTERSECTION:
+      while (samples--)
+        {
+          gint b;
+
+          for (b = RED; b < ALPHA; b++)
+            out[b] = in[b];
+
+          out[ALPHA] = 0.0f;
+
+          in  += 4;
+          out += 4;
+        }
+      break;
+    }
+
+  return TRUE;
+}
+
+static GimpLayerCompositeRegion
+gimp_operation_replace_get_affected_region (GimpOperationLayerMode *layer_mode)
+{
+  GimpLayerCompositeRegion affected_region = GIMP_LAYER_COMPOSITE_REGION_INTERSECTION;
+
+  if (layer_mode->opacity != 0.0)
+    affected_region |= GIMP_LAYER_COMPOSITE_REGION_DESTINATION;
+
+  /* if opacity != 1.0, or we have a mask, then we also affect SOURCE, but this
+   * is considered the case anyway, so no need for special handling.
+   */
+
+  return affected_region;
+}

app/operations/layer-modes/gimpoperationreplace.h

@@ -0,0 +1,53 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationreplace.h
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_REPLACE_H__
+#define __GIMP_OPERATION_REPLACE_H__
+
+
+#include "gimpoperationlayermode.h"
+
+
+#define GIMP_TYPE_OPERATION_REPLACE            (gimp_operation_replace_get_type ())
+#define GIMP_OPERATION_REPLACE(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_OPERATION_REPLACE, GimpOperationReplace))
+#define GIMP_OPERATION_REPLACE_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  GIMP_TYPE_OPERATION_REPLACE, GimpOperationReplaceClass))
+#define GIMP_IS_OPERATION_REPLACE(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_OPERATION_REPLACE))
+#define GIMP_IS_OPERATION_REPLACE_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  GIMP_TYPE_OPERATION_REPLACE))
+#define GIMP_OPERATION_REPLACE_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  GIMP_TYPE_OPERATION_REPLACE, GimpOperationReplaceClass))
+
+
+typedef struct _GimpOperationReplace      GimpOperationReplace;
+typedef struct _GimpOperationReplaceClass GimpOperationReplaceClass;
+
+struct _GimpOperationReplace
+{
+  GimpOperationLayerMode parent_instance;
+};
+
+struct _GimpOperationReplaceClass
+{
+  GimpOperationLayerModeClass parent_class;
+};
+
+
+GType   gimp_operation_replace_get_type (void) G_GNUC_CONST;
+
+
+#endif /* __GIMP_OPERATION_REPLACE_H__ */

app/operations/layer-modes/gimpoperationsplit.c

@@ -0,0 +1,213 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationsplit.c
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *               2017 Ell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl-plugin.h>
+
+#include "../operations-types.h"
+
+#include "gimpoperationsplit.h"
+
+
+static gboolean   gimp_operation_split_process (GeglOperation       *op,
+                                                void                *in,
+                                                void                *layer,
+                                                void                *mask,
+                                                void                *out,
+                                                glong                samples,
+                                                const GeglRectangle *roi,
+                                                gint                 level);
+
+
+G_DEFINE_TYPE (GimpOperationSplit, gimp_operation_split,
+               GIMP_TYPE_OPERATION_LAYER_MODE)
+
+
+static void
+gimp_operation_split_class_init (GimpOperationSplitClass *klass)
+{
+  GeglOperationClass          *operation_class  = GEGL_OPERATION_CLASS (klass);
+  GimpOperationLayerModeClass *layer_mode_class = GIMP_OPERATION_LAYER_MODE_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name",        "gimp:split",
+                                 "description", "GIMP split mode operation",
+                                 NULL);
+
+  layer_mode_class->process = gimp_operation_split_process;
+}
+
+static void
+gimp_operation_split_init (GimpOperationSplit *self)
+{
+}
+
+static gboolean
+gimp_operation_split_process (GeglOperation       *op,
+                              void                *in_p,
+                              void                *layer_p,
+                              void                *mask_p,
+                              void                *out_p,
+                              glong                samples,
+                              const GeglRectangle *roi,
+                              gint                 level)
+{
+  GimpOperationLayerMode *layer_mode = (gpointer) op;
+  gfloat                 *in         = in_p;
+  gfloat                 *out        = out_p;
+  gfloat                 *layer      = layer_p;
+  gfloat                 *mask       = mask_p;
+  gfloat                  opacity    = layer_mode->opacity;
+  const gboolean          has_mask   = mask != NULL;
+
+  switch (layer_mode->real_composite_mode)
+    {
+    case GIMP_LAYER_COMPOSITE_UNION:
+      while (samples--)
+        {
+          gfloat in_alpha    = in[ALPHA];
+          gfloat layer_alpha = layer[ALPHA] * opacity;
+          gfloat new_alpha;
+          gint   b;
+
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          if (layer_alpha <= in_alpha)
+            {
+              new_alpha = in_alpha - layer_alpha;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+          else
+            {
+              new_alpha = layer_alpha - in_alpha;
+
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b];
+                }
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+    case GIMP_LAYER_COMPOSITE_AUTO:
+      while (samples--)
+        {
+          gfloat in_alpha    = in[ALPHA];
+          gfloat layer_alpha = layer[ALPHA] * opacity;
+          gfloat new_alpha;
+          gint   b;
+
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          new_alpha = MAX (in_alpha - layer_alpha, 0.0f);
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b];
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+      while (samples--)
+        {
+          gfloat in_alpha    = in[ALPHA];
+          gfloat layer_alpha = layer[ALPHA] * opacity;
+          gfloat new_alpha;
+          gint   b;
+
+          if (has_mask)
+            layer_alpha *= *mask;
+
+          new_alpha = MAX (layer_alpha - in_alpha, 0.0f);
+
+          if (new_alpha != 0.0f)
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = layer[b];
+                }
+            }
+          else
+            {
+              for (b = RED; b < ALPHA; b++)
+                {
+                  out[b] = in[b];
+                }
+            }
+
+          out[ALPHA] = new_alpha;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+
+          if (has_mask)
+            mask++;
+        }
+      break;
+
+    case GIMP_LAYER_COMPOSITE_INTERSECTION:
+      while (samples--)
+        {
+          gint   b;
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b];
+            }
+
+          out[ALPHA] = 0.0f;
+
+          in    += 4;
+          out   += 4;
+        }
+      break;
+    }
+
+  return TRUE;
+}

app/operations/layer-modes/gimpoperationsplit.h

@@ -0,0 +1,54 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationsplit.h
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *               2017 Ell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_OPERATION_SPLIT_H__
+#define __GIMP_OPERATION_SPLIT_H__
+
+
+#include "gimpoperationlayermode.h"
+
+
+#define GIMP_TYPE_OPERATION_SPLIT            (gimp_operation_split_get_type ())
+#define GIMP_OPERATION_SPLIT(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_OPERATION_SPLIT, GimpOperationSplit))
+#define GIMP_OPERATION_SPLIT_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  GIMP_TYPE_OPERATION_SPLIT, GimpOperationSplitClass))
+#define GIMP_IS_OPERATION_SPLIT(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_OPERATION_SPLIT))
+#define GIMP_IS_OPERATION_SPLIT_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  GIMP_TYPE_OPERATION_SPLIT))
+#define GIMP_OPERATION_SPLIT_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  GIMP_TYPE_OPERATION_SPLIT, GimpOperationSplitClass))
+
+
+typedef struct _GimpOperationSplit      GimpOperationSplit;
+typedef struct _GimpOperationSplitClass GimpOperationSplitClass;
+
+struct _GimpOperationSplit
+{
+  GimpOperationLayerMode  parent_instance;
+};
+
+struct _GimpOperationSplitClass
+{
+  GimpOperationLayerModeClass  parent_class;
+};
+
+
+GType   gimp_operation_split_get_type (void) G_GNUC_CONST;
+
+
+#endif /* __GIMP_OPERATION_SPLIT_H__ */