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app: when creating palette only snap to black/white when present

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By only doing the snapping to white/black for whitest/blackest palette
entries when the original RGB data contained these colors we permit
choosing near white/black colors in the cases where this might be
a desirable result as the whitest/blackest colors.
This commit is contained in:
Øyvind Kolås
2020-05-01 02:19:15 +02:00
parent 9bb3ff42d7
commit d4387987b5
1 changed files with 22 additions and 2 deletions
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24
app/core/gimpimage-convert-indexed.c
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@ -544,6 +544,8 @@ static void compute_color_lin8 (QuantizeObj *quantobj,
static guchar found_cols[MAXNUMCOLORS][3]; static guchar found_cols[MAXNUMCOLORS][3];
static gint num_found_cols; static gint num_found_cols;
static gboolean needs_quantize; static gboolean needs_quantize;
static gboolean had_white;
static gboolean had_black;
/**********************************************************/ /**********************************************************/
@ -851,6 +853,8 @@ gimp_image_convert_indexed (GimpImage *image,
* need to quantize or color-dither. * need to quantize or color-dither.
*/ */
needs_quantize = FALSE; needs_quantize = FALSE;
had_black = FALSE;
had_white = FALSE;
num_found_cols = 0; num_found_cols = 0;
/* Build the histogram */ /* Build the histogram */
@ -1162,6 +1166,18 @@ generate_histogram_gray (CFHistogram histogram,
} }
} }
static void
check_white_or_black (const guchar *data)
{
if (data[RED] == 255 &&
data[GREEN] == 255 &&
data[BLUE] == 255)
had_white = TRUE;
if (data[RED] ==0 &&
data[GREEN]==0 &&
data[BLUE] ==0)
had_black = TRUE;
}
static void static void
generate_histogram_rgb (CFHistogram histogram, generate_histogram_rgb (CFHistogram histogram,
@ -1241,6 +1257,7 @@ generate_histogram_rgb (CFHistogram histogram,
data[RED], data[RED],
data[GREEN], data[GREEN],
data[BLUE]); data[BLUE]);
check_white_or_black (data);
(*colfreq)++; (*colfreq)++;
} }
@ -1265,6 +1282,7 @@ generate_histogram_rgb (CFHistogram histogram,
data[RED], data[RED],
data[GREEN], data[GREEN],
data[BLUE]); data[BLUE]);
check_white_or_black (data);
(*colfreq)++; (*colfreq)++;
} }
@ -1342,6 +1360,8 @@ generate_histogram_rgb (CFHistogram histogram,
found_cols[num_found_cols-1][0] = data[RED]; found_cols[num_found_cols-1][0] = data[RED];
found_cols[num_found_cols-1][1] = data[GREEN]; found_cols[num_found_cols-1][1] = data[GREEN];
found_cols[num_found_cols-1][2] = data[BLUE]; found_cols[num_found_cols-1][2] = data[BLUE];
check_white_or_black (data);
} }
} }
} }
@ -2796,13 +2816,13 @@ snap_to_black_and_white (QuantizeObj *quantobj)
} }
} }
if (white_dist < POW2(24)) /* 24 units in sRGB ~= deltaE of 9.5 */ if (had_white && white_dist < POW2(32))
{ {
quantobj->cmap[whitest].red = quantobj->cmap[whitest].red =
quantobj->cmap[whitest].green = quantobj->cmap[whitest].green =
quantobj->cmap[whitest].blue = 255; quantobj->cmap[whitest].blue = 255;
} }
if (black_dist < POW2(24)) if (had_black && black_dist < POW2(32))
{ {
quantobj->cmap[blackest].red = quantobj->cmap[blackest].red =
quantobj->cmap[blackest].green = quantobj->cmap[blackest].green =