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12b2abce7c
This is used for the gimp_color_is_perceptually_identical() function, because the Euclidean distance in LCH is extremely limited, if not wrong in many cases. Indeed LCH is not perfectly perceptually uniform, and for this exact reason, the CIE defined the specific Delta E algorithms. Later versions are also based on LCH values, so my intuition to use it for distance was on a good start, yet these algorithms were refined a few times to allow for corrections in perceptual uniformity imperfections. This was in particular needed to verify if a color is out of a CMYK space gamut. The idea is to compare the distance of the RGB (or other) and the CMYK version, since we cannot just check if the CMYK color is out of the [0; 1] range (it never is). Instead if both colors are perceptually identical, then we consider that the RGB color was inside the CMYK space gamut. The naive algorithm was giving any (or nearly) color as out-of-gamut. Now using CIEDE2000, I get a much nicer results.
70 lines
2.4 KiB
C
70 lines
2.4 KiB
C
/* LIBGIMP - The GIMP Library
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* Copyright (C) 1995-1997 Peter Mattis and Spencer Kimball
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*
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* This library is free software: you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 3 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see
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* <https://www.gnu.org/licenses/>.
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*/
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#ifndef __GIMP_COLOR_H__
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#define __GIMP_COLOR_H__
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#define __GIMP_COLOR_H_INSIDE__
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#include <libgimpcolor/gimpcolortypes.h>
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#include <libgimpcolor/gimpadaptivesupersample.h>
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#include <libgimpcolor/gimpbilinear.h>
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#include <libgimpcolor/gimpcairo.h>
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#include <libgimpcolor/gimpcolormanaged.h>
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#include <libgimpcolor/gimpcolorprofile.h>
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#include <libgimpcolor/gimpcolorspace.h>
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#include <libgimpcolor/gimpcolortransform.h>
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#include <libgimpcolor/gimpcmyk.h>
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#include <libgimpcolor/gimphsl.h>
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#include <libgimpcolor/gimphsv.h>
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#include <libgimpcolor/gimppixbuf.h>
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#include <libgimpcolor/gimprgb.h>
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#undef __GIMP_COLOR_H_INSIDE__
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G_BEGIN_DECLS
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/*
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* GEGL_TYPE_COLOR
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*/
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#define GIMP_VALUE_HOLDS_COLOR(value) (G_TYPE_CHECK_VALUE_TYPE ((value), GEGL_TYPE_COLOR))
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void gimp_color_set_alpha (GeglColor *color,
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gdouble alpha);
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gboolean gimp_color_is_perceptually_identical (GeglColor *color1,
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GeglColor *color2);
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GeglColor * gimp_color_parse_css (const gchar *css,
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gint len);
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GeglColor * gimp_color_parse_hex (const gchar *hex,
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gint len);
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GeglColor * gimp_color_parse_name (const gchar *name,
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gint len);
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gboolean gimp_color_is_out_of_self_gamut (GeglColor *color);
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gboolean gimp_color_is_out_of_gamut (GeglColor *color,
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const Babl *space);
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G_END_DECLS
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#endif /* __GIMP_COLOR_H__ */
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