app: added gegl erase mode

app/gegl/gimp-gegl-nodes.c

@@ -324,7 +324,6 @@ gimp_gegl_node_set_layer_mode (GeglNode             *node,
     case GIMP_COLOR_MODE:
     case GIMP_VALUE_MODE:
     case GIMP_COLOR_ERASE_MODE:
-    case GIMP_ERASE_MODE:
     case GIMP_ANTI_ERASE_MODE:
       gegl_node_set (node,
                      "operation",     "gimp:point-layer-mode",

app/gegl/gimpoperationerasemode.c

@@ -3,6 +3,7 @@
  *
  * gimpoperationerasemode.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
@@ -72,21 +73,45 @@ gimp_operation_erase_mode_process (GeglOperation       *operation,
                                    const GeglRectangle *roi,
                                    gint                 level)
 {
+  GimpOperationPointLayerMode *point = GIMP_OPERATION_POINT_LAYER_MODE (operation);
   gfloat                      *in    = in_buf;
   gfloat                      *layer = aux_buf;
   gfloat                      *out   = out_buf;
 
+  if (point->premultiplied)
+    {
       while (samples--)
         {
-      out[RED]   = in[RED];
+          gint b;
-      out[GREEN] = in[GREEN];
+
-      out[BLUE]  = in[BLUE];
+          out[ALPHA] = in[ALPHA] - in[ALPHA] * layer[ALPHA];
-      out[ALPHA] = in[ALPHA];
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b] / in[ALPHA] * out[ALPHA];
+            }
 
           in    += 4;
           layer += 4;
           out   += 4;
         }
+    }
+  else
+    {
+      while (samples--)
+        {
+          gint b;
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b];
+            }
+          out[ALPHA] = in[ALPHA] - in[ALPHA] * layer[ALPHA];;
+
+          in    += 4;
+          layer += 4;
+          out   += 4;
+        }
+    }
 
   return TRUE;
 }