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libgimpcolor: gimp_color_is_perceptually_identical() should also check transparency.

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This fixes weird behavior when changing only the alpha value of a color, e.g. in
the channel color GUI. The before and after colors were considered the same. Now
they won't.
This commit is contained in:
Jehan 2023-11-20 16:46:56 +01:00
parent 4879ab7b7f
commit 7d2d96a0da
1 changed files with 22 additions and 7 deletions
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29
libgimpcolor/gimpcolor.c
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@ -92,6 +92,20 @@ gimp_color_set_alpha (GeglColor *color,
* human eyes, by computing the distance in a color space as perceptually * human eyes, by computing the distance in a color space as perceptually
* uniform as possible. * uniform as possible.
* *
* This function will also consider any transparency channel, so that if you
* only want to compare the pure color, you could for instance set both color's
* alpha channel to 1.0 first (possibly on duplicates of the colors if originals
* should not be modified), such as:
*
* ```C
* gimp_color_set_alpha (color1, 1.0);
* gimp_color_set_alpha (color2, 1.0);
* if (gimp_color_is_perceptually_identical (color1, color2))
* {
* printf ("Both colors are identical, ignoring their alpha component");
* }
* ```
*
* Returns: whether the 2 colors can be considered the same for the human eyes. * Returns: whether the 2 colors can be considered the same for the human eyes.
* *
* Since: 3.0 * Since: 3.0
@ -100,8 +114,8 @@ gboolean
gimp_color_is_perceptually_identical (GeglColor *color1, gimp_color_is_perceptually_identical (GeglColor *color1,
GeglColor *color2) GeglColor *color2)
{ {
gfloat pixel1[3]; gfloat pixel1[4];
gfloat pixel2[3]; gfloat pixel2[4];
g_return_val_if_fail (GEGL_IS_COLOR (color1), FALSE); g_return_val_if_fail (GEGL_IS_COLOR (color1), FALSE);
g_return_val_if_fail (GEGL_IS_COLOR (color2), FALSE); g_return_val_if_fail (GEGL_IS_COLOR (color2), FALSE);
@ -109,8 +123,8 @@ gimp_color_is_perceptually_identical (GeglColor *color1,
/* CIE LCh space is considered quite perceptually uniform, a bit better than /* CIE LCh space is considered quite perceptually uniform, a bit better than
* Lab on this aspect, AFAIU. * Lab on this aspect, AFAIU.
*/ */
gegl_color_get_pixel (color1, babl_format ("CIE LCH(ab) float"), pixel1); gegl_color_get_pixel (color1, babl_format ("CIE LCH(ab) alpha float"), pixel1);
gegl_color_get_pixel (color2, babl_format ("CIE LCH(ab) float"), pixel2); gegl_color_get_pixel (color2, babl_format ("CIE LCH(ab) alpha float"), pixel2);
/* This is not a proper distance computation, but is acceptable for our use /* This is not a proper distance computation, but is acceptable for our use
* case while being simpler. While we used to use 1e-6 as threshold with float * case while being simpler. While we used to use 1e-6 as threshold with float
@ -118,8 +132,9 @@ gimp_color_is_perceptually_identical (GeglColor *color1,
* wide gamut spaces. This is why use the threshold is 1e-4 right now. * wide gamut spaces. This is why use the threshold is 1e-4 right now.
*/ */
#define SQR(x) ((x) * (x)) #define SQR(x) ((x) * (x))
return (SQR (pixel1[0] - pixel2[0]) + return (ABS (pixel1[3] - pixel2[3]) <= 1e-4 &&
SQR (pixel1[1] - pixel2[1]) + (SQR (pixel1[0] - pixel2[0]) +
SQR (pixel1[2] - pixel2[2]) <= 1e-4); SQR (pixel1[1] - pixel2[1]) +
SQR (pixel1[2] - pixel2[2]) <= 1e-4));
#undef SQR #undef SQR
} }