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app: add handling of CIE Lab blend space to gradient 

Using CIE Lab yields gradients that more closely resemble the perceptual
gradients but without the gamma based blending problems of linear-RGB / CIE
XYZ.
This commit is contained in:
Øyvind Kolås 2018-04-14 18:11:57 +02:00
parent e007da2604
commit 6d6da684f1
1 changed files with 30 additions and 8 deletions
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38
app/core/gimpgradient.c
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@ -100,6 +100,8 @@ G_DEFINE_TYPE_WITH_CODE (GimpGradient, gimp_gradient, GIMP_TYPE_DATA,
static const Babl *fish_srgb_to_linear_rgb = NULL;
static const Babl *fish_linear_rgb_to_srgb = NULL;
static const Babl *fish_srgb_to_cie_lab = NULL;
static const Babl *fish_cie_lab_a_to_srgb = NULL;
static void
@ -128,6 +130,10 @@ gimp_gradient_class_init (GimpGradientClass *klass)
babl_format ("RGB double"));
fish_linear_rgb_to_srgb = babl_fish (babl_format ("RGBA double"),
babl_format ("R'G'B'A double"));
fish_srgb_to_cie_lab = babl_fish (babl_format ("R'G'B' double"),
babl_format ("CIE Lab double"));
fish_cie_lab_a_to_srgb = babl_fish (babl_format ("CIE Lab alpha double"),
babl_format ("R'G'B'A double"));
}
static void
@ -514,22 +520,38 @@ gimp_gradient_get_color_at (GimpGradient *gradient,
if (seg->color == GIMP_GRADIENT_SEGMENT_RGB)
{
if (blend_color_space == GIMP_GRADIENT_BLEND_RGB_LINEAR)
switch (blend_color_space)
{
babl_process (fish_srgb_to_linear_rgb,
&left_color, &left_color, 1);
babl_process (fish_srgb_to_linear_rgb,
&right_color, &right_color, 1);
case GIMP_GRADIENT_BLEND_CIE_LAB:
babl_process (fish_srgb_to_cie_lab,
&left_color, &left_color, 1);
babl_process (fish_srgb_to_cie_lab,
&right_color, &right_color, 1);
break;
case GIMP_GRADIENT_BLEND_RGB_LINEAR:
babl_process (fish_srgb_to_linear_rgb,
&left_color, &left_color, 1);
babl_process (fish_srgb_to_linear_rgb,
&right_color, &right_color, 1);
case GIMP_GRADIENT_BLEND_RGB_PERCEPTUAL:
break;
}
rgb.r = left_color.r + (right_color.r - left_color.r) * factor;
rgb.g = left_color.g + (right_color.g - left_color.g) * factor;
rgb.b = left_color.b + (right_color.b - left_color.b) * factor;
if (blend_color_space == GIMP_GRADIENT_BLEND_RGB_LINEAR)
switch (blend_color_space)
{
babl_process (fish_linear_rgb_to_srgb,
&rgb, &rgb, 1);
case GIMP_GRADIENT_BLEND_CIE_LAB:
babl_process (fish_cie_lab_a_to_srgb,
&rgb, &rgb, 1);
break;
case GIMP_GRADIENT_BLEND_RGB_LINEAR:
babl_process (fish_linear_rgb_to_srgb,
&rgb, &rgb, 1);
case GIMP_GRADIENT_BLEND_RGB_PERCEPTUAL:
break;
}
}
else