[babl] Modify CIE color space conversions to use D50-adapted sRGB
- From: Øyvind Kolås <ok src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [babl] Modify CIE color space conversions to use D50-adapted sRGB
- Date: Tue, 30 Dec 2014 02:08:57 +0000 (UTC)
commit 0dba0608bd2cfe69453834c1ec87b7a2be13d2dd
Author: Elle Stone <ellestone ninedegreesbelow com>
Date: Mon Dec 29 16:42:50 2014 -0500
Modify CIE color space conversions to use D50-adapted sRGB
extensions/CIE.c | 988 +++++++++++++++++++-----------------------------------
1 files changed, 349 insertions(+), 639 deletions(-)
---
diff --git a/extensions/CIE.c b/extensions/CIE.c
index e728f7c..8533cb7 100644
--- a/extensions/CIE.c
+++ b/extensions/CIE.c
@@ -54,6 +54,9 @@ components (void)
babl_component_new ("CIE b", "chroma", NULL);
babl_component_new ("CIE C(ab)", "chroma", NULL);
babl_component_new ("CIE H(ab)", "chroma", NULL);
+ /* babl_component_new ("CIE X", NULL);
+ babl_component_new ("CIE Y", NULL);
+ babl_component_new ("CIE Z", NULL);*/
}
static void
@@ -88,69 +91,57 @@ models (void)
babl_component ("CIE H(ab)"),
babl_component ("A"),
NULL);
+ /*babl_model_new (
+ "name", "CIE XYZ",
+ babl_component ("CIE X"),
+ babl_component ("CIE Y"),
+ babl_component ("CIE Z"),
+ NULL);*/
}
-/*********** cpercep.h ********* */
+/*********** RGB/CIE color space conversions ********* */
-/*
- Copyright (C) 1997-2002 Adam D. Moss (the "Author"). All Rights Reserved.
+static void rgbcie_init (void);
- Permission is hereby granted, free of charge, to any person obtaining a copy
- of this software and associated documentation files (the "Software"), to deal
- in the Software without restriction, including without limitation the rights
- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- copies of the Software, and to permit persons to whom the Software is fur-
- nished to do so, subject to the following conditions:
-
- The above copyright notice and this permission notice shall be included in
- all copies or substantial portions of the Software.
-
- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FIT-
- NESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
- IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CON-
- NECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-
- Except as contained in this notice, the name of the Author of the
- Software shall not be used in advertising or otherwise to promote the sale,
- use or other dealings in this Software without prior written authorization
- from the Author.
- */
-
-/*
- cpercep.c: The CPercep Functions v0.9: 2002-02-10
- Adam D. Moss: adam gimp org <http://www.foxbox.org/adam/code/cpercep/>
-
- TODO: document functions, rename erroneously-named arguments
- */
-
-static void cpercep_init (void);
-
-static void cpercep_rgb_to_space (double inr,
- double ing,
- double inb,
- double *outr,
- double *outg,
- double *outb);
-
-static void cpercep_space_to_rgb (double inr,
- double ing,
- double inb,
- double *outr,
- double *outg,
- double *outb);
-
-static void ab_to_chab (double a,
+static void ab_to_CHab (double a,
double b,
- double *C,
- double *H);
+ double *to_C,
+ double *to_H);
-static void chab_to_ab (double C,
+static void CHab_to_ab (double C,
double H,
- double *a,
- double *b);
-
+ double *to_a,
+ double *to_b);
+
+static void RGB_to_XYZ (double R,
+ double G,
+ double B,
+ double *to_X,
+ double *to_Y,
+ double *to_Z);
+
+static void XYZ_to_LAB (double X,
+ double Y,
+ double Z,
+ double *to_L,
+ double *to_a,
+ double *to_b
+ );
+
+static void LAB_to_XYZ (double L,
+ double a,
+ double b,
+ double *to_X,
+ double *to_Y,
+ double *to_Z
+ );
+
+static void XYZ_to_RGB (double X,
+ double Y,
+ double Z,
+ double *to_R,
+ double *to_G,
+ double *to_B);
static long
rgba_to_lab (char *src,
@@ -159,13 +150,16 @@ rgba_to_lab (char *src,
{
while (n--)
{
- double red = ((double *) src)[0];
- double green = ((double *) src)[1];
- double blue = ((double *) src)[2];
-
- double L, a, b;
-
- cpercep_rgb_to_space (red, green, blue, &L, &a, &b);
+ double R = ((double *) src)[0];
+ double G = ((double *) src)[1];
+ double B = ((double *) src)[2];
+ double X, Y, Z, L, a, b;
+
+ //convert RGB to XYZ
+ RGB_to_XYZ (R, G, B, &X, &Y, &Z);
+
+ //convert XYZ to Lab
+ XYZ_to_LAB (X, Y, Z, &L, &a, &b);
((double *) dst)[0] = L;
((double *) dst)[1] = a;
@@ -188,13 +182,16 @@ lab_to_rgba (char *src,
double a = ((double *) src)[1];
double b = ((double *) src)[2];
- double red, green, blue;
-
- cpercep_space_to_rgb (L, a, b, &red, &green, &blue);
-
- ((double *) dst)[0] = red;
- ((double *) dst)[1] = green;
- ((double *) dst)[2] = blue;
+ double X, Y, Z, R, G, B;
+
+ //convert Lab to XYZ
+ LAB_to_XYZ (L, a, b, &X, &Y, &Z);
+
+ //convert XYZ to RGB
+ XYZ_to_RGB (X, Y, Z, &R, &G, &B);
+ ((double *) dst)[0] = R;
+ ((double *) dst)[1] = G;
+ ((double *) dst)[2] = B;
((double *) dst)[3] = 1.0;
src += sizeof (double) * 3;
@@ -211,14 +208,17 @@ rgba_to_laba (char *src,
{
while (n--)
{
- double red = ((double *) src)[0];
- double green = ((double *) src)[1];
- double blue = ((double *) src)[2];
+ double R = ((double *) src)[0];
+ double G = ((double *) src)[1];
+ double B = ((double *) src)[2];
double alpha = ((double *) src)[3];
-
- double L, a, b;
-
- cpercep_rgb_to_space (red, green, blue, &L, &a, &b);
+ double X, Y, Z, L, a, b;
+
+ //convert RGB to XYZ
+ RGB_to_XYZ (R, G, B, &X, &Y, &Z);
+
+ //convert XYZ to Lab
+ XYZ_to_LAB (X, Y, Z, &L, &a, &b);
((double *) dst)[0] = L;
((double *) dst)[1] = a;
@@ -243,13 +243,16 @@ laba_to_rgba (char *src,
double b = ((double *) src)[2];
double alpha = ((double *) src)[3];
- double red, green, blue;
-
- cpercep_space_to_rgb (L, a, b, &red, &green, &blue);
-
- ((double *) dst)[0] = red;
- ((double *) dst)[1] = green;
- ((double *) dst)[2] = blue;
+ double X, Y, Z, R, G, B;
+
+ //convert Lab to XYZ
+ LAB_to_XYZ (L, a, b, &X, &Y, &Z);
+
+ //convert XYZ to RGB
+ XYZ_to_RGB (X, Y, Z, &R, &G, &B);
+ ((double *) dst)[0] = R;
+ ((double *) dst)[1] = G;
+ ((double *) dst)[2] = B;
((double *) dst)[3] = alpha;
src += sizeof (double) * 4;
@@ -258,8 +261,30 @@ laba_to_rgba (char *src,
return n;
}
+static void
+CHab_to_ab (double C,
+ double H,
+ double *to_a,
+ double *to_b)
+{
+ *to_a = cos (H * RADIANS_PER_DEGREE) * C;
+ *to_b = sin (H * RADIANS_PER_DEGREE) * C;
+}
+static void
+ab_to_CHab (double a,
+ double b,
+ double *to_C,
+ double *to_H)
+{
+ *to_C = sqrt ( (a * a) + (b * b) );
+ *to_H = atan2 (b, a) * DEGREES_PER_RADIAN;
+ // Keep H within the range 0-360
+ if (*to_H < 0.0)
+ *to_H += 360;
+
+}
static long
rgba_to_lchab (char *src,
@@ -268,13 +293,19 @@ rgba_to_lchab (char *src,
{
while (n--)
{
- double red = ((double *) src)[0];
- double green = ((double *) src)[1];
- double blue = ((double *) src)[2];
- double L, a, b, C, H;
-
- cpercep_rgb_to_space (red, green, blue, &L, &a, &b);
- ab_to_chab (a, b, &C, &H);
+ double R = ((double *) src)[0];
+ double G = ((double *) src)[1];
+ double B = ((double *) src)[2];
+ double X, Y, Z, L, a, b, C, H;
+
+ //convert RGB to XYZ
+ RGB_to_XYZ (R, G, B, &X, &Y, &Z);
+
+ //convert XYZ to Lab
+ XYZ_to_LAB (X, Y, Z, &L, &a, &b);
+
+ //convert Lab to LCH(ab)
+ ab_to_CHab (a, b, &C, &H);
((double *) dst)[0] = L;
((double *) dst)[1] = C;
@@ -296,14 +327,20 @@ lchab_to_rgba (char *src,
double L = ((double *) src)[0];
double C = ((double *) src)[1];
double H = ((double *) src)[2];
- double a, b, red, green, blue;
-
- chab_to_ab (C, H, &a, &b);
- cpercep_space_to_rgb (L, a, b, &red, &green, &blue);
-
- ((double *) dst)[0] = red;
- ((double *) dst)[1] = green;
- ((double *) dst)[2] = blue;
+ double a, b, X, Y, Z, R, G, B;
+
+ //Convert LCH(ab) to Lab
+ CHab_to_ab (C, H, &a, &b);
+
+ //Convert LAB to XYZ
+ LAB_to_XYZ (L, a, b, &X, &Y, &Z);
+
+ //Convert XYZ to RGB
+ XYZ_to_RGB (X, Y, Z, &R, &G, &B);
+
+ ((double *) dst)[0] = R;
+ ((double *) dst)[1] = G;
+ ((double *) dst)[2] = B;
((double *) dst)[3] = 1.0;
src += sizeof (double) * 3;
@@ -320,14 +357,20 @@ rgba_to_lchaba (char *src,
{
while (n--)
{
- double red = ((double *) src)[0];
- double green = ((double *) src)[1];
- double blue = ((double *) src)[2];
+ double R = ((double *) src)[0];
+ double G = ((double *) src)[1];
+ double B = ((double *) src)[2];
double alpha = ((double *) src)[3];
- double L, a, b, C, H;
+ double X, Y, Z, L, a, b, C, H;
- cpercep_rgb_to_space (red, green, blue, &L, &a, &b);
- ab_to_chab (a, b, &C, &H);
+ //convert RGB to XYZ
+ RGB_to_XYZ (R, G, B, &X, &Y, &Z);
+
+ //convert XYZ to Lab
+ XYZ_to_LAB (X, Y, Z, &L, &a, &b);
+
+ //convert Lab to LCH(ab)
+ ab_to_CHab (a, b, &C, &H);
((double *) dst)[0] = L;
((double *) dst)[1] = C;
@@ -351,14 +394,20 @@ lchaba_to_rgba (char *src,
double C = ((double *) src)[1];
double H = ((double *) src)[2];
double alpha = ((double *) src)[3];
- double a, b, red, green, blue;
-
- chab_to_ab (C, H, &a, &b);
- cpercep_space_to_rgb (L, a, b, &red, &green, &blue);
-
- ((double *) dst)[0] = red;
- ((double *) dst)[1] = green;
- ((double *) dst)[2] = blue;
+ double a, b, X, Y, Z, R, G, B;
+
+ //Convert LCH(ab) to Lab
+ CHab_to_ab (C, H, &a, &b);
+
+ //Convert Lab to XYZ
+ LAB_to_XYZ (L, a, b, &X, &Y, &Z);
+
+ //Convert XYZ to RGB
+ XYZ_to_RGB (X, Y, Z, &R, &G, &B);
+
+ ((double *) dst)[0] = R;
+ ((double *) dst)[1] = G;
+ ((double *) dst)[2] = B;
((double *) dst)[3] = alpha;
src += sizeof (double) * 4;
@@ -419,8 +468,20 @@ conversions (void)
"linear", lchaba_to_rgba,
NULL
);
+ /*babl_conversion_new (
+ babl_model ("RGBA"),
+ babl_model ("CIE XYZ"),
+ "linear", RGB_to_XYZ,
+ NULL
+ );
+ babl_conversion_new (
+ babl_model ("CIE XYZ"),
+ babl_model ("RGBA"),
+ "linear", XYZ_to_RGB,
+ NULL
+ );*/
- cpercep_init ();
+ rgbcie_init ();
}
static void
@@ -435,6 +496,16 @@ formats (void)
babl_component ("CIE a"),
babl_component ("CIE b"),
NULL);
+
+ /*babl_format_new (
+ "name", "CIE XYZ float",
+ babl_model ("CIE XYZ"),
+
+ babl_type ("float"),
+ babl_component ("CIE X"),
+ babl_component ("CIE Y"),
+ babl_component ("CIE Z"),
+ NULL);*/
babl_format_new (
"name", "CIE Lab alpha float",
@@ -781,68 +852,6 @@ types (void)
types_u16 ();
}
-
-
-
-/*********** cpercep.c ********* */
-
-
-/*
- Copyright (C) 1999-2002 Adam D. Moss (the "Author"). All Rights Reserved.
-
- Permission is hereby granted, free of charge, to any person obtaining a copy
- of this software and associated documentation files (the "Software"), to deal
- in the Software without restriction, including without limitation the rights
- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- copies of the Software, and to permit persons to whom the Software is fur-
- nished to do so, subject to the following conditions:
-
- The above copyright notice and this permission notice shall be included in
- all copies or substantial portions of the Software.
-
- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FIT-
- NESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
- IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CON-
- NECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-
- Except as contained in this notice, the name of the Author of the
- Software shall not be used in advertising or otherwise to promote the sale,
- use or other dealings in this Software without prior written authorization
- from the Author.
- */
-
-/*
- cpercep.c: The CPercep Functions v0.9: 2002-02-10
- Adam D. Moss: adam gimp org <http://www.foxbox.org/adam/code/cpercep/>
-
- This code module concerns itself with conversion from a hard-coded
- RGB colour space (sRGB by default) to CIE L*a*b* and back again with
- (primarily) precision and (secondarily) speed, oriented largely
- towards the purposes of quantifying the PERCEPTUAL difference between
- two arbitrary RGB colours with a minimum of fuss.
-
- Motivation One: The author is disheartened at the amount of graphics
- processing software around which uses weighted or non-weighted
- Euclidean distance between co-ordinates within a (poorly-defined) RGB
- space as the basis of what should really be an estimate of perceptual
- difference to the human eye. Certainly it's fast to do it that way,
- but please think carefully about whether your particular application
- should be tolerating sloppy results for the sake of real-time response.
-
- Motivation Two: Lack of tested, re-usable and free code available
- for this purpose. The difficulty in finding something similar to
- CPercep with a free license motivated this project; I hope that this
- code also serves to illustrate how to perform the
- R'G'B'->XYZ->L*a*b*->XYZ->R'G'B' transformation correctly since I
- was distressed to note how many of the equations and code snippets
- on the net were omitting the reverse transform and/or were using
- incorrectly-derived or just plain wrong constants.
-
- TODO: document functions, rename erroneously-named arguments
- */
-
/* defines added to make it compile outside gimp */
#ifndef gboolean
@@ -859,339 +868,197 @@ types (void)
/* #include "config.h" */
#include <math.h>
-#ifndef __GLIBC__
-/* cbrt() is a GNU extension */
-#define cbrt(x) (pow (x, 1.0 / 3.0))
-#endif
-
-
-/* defines:
-
- SANITY: emits warnings when passed non-sane colours (and usually
- corrects them) -- useful when debugging.
-
- APPROX: speeds up the conversion from RGB to the colourspace by
- assuming that the RGB values passed in are integral and definitely
- in the range 0->255
- */
-
-/* #define SANITY */
-/* #define APPROX */
-
-
-/* define characteristics of the source RGB space (and the space
- within which we try to behave linearly). */
-
-/* Phosphor colours: */
-
-/* sRGB/HDTV phosphor colours */
-static const double pxr = 0.64;
-static const double pyr = 0.33;
-static const double pxg = 0.30;
-static const double pyg = 0.60;
-static const double pxb = 0.15;
-static const double pyb = 0.06;
-
-/* White point: */
-
-/* D65 (6500K) (recommended but not a common display default) */
-static const double lxn = 0.312713;
-static const double lyn = 0.329016;
-
-/* D50 (5000K) */
-/*static const double lxn = 0.3457; */
-/*static const double lyn = 0.3585; */
-
-/* D55 (5500K) */
-/*static const double lxn = 0.3324; */
-/*static const double lyn = 0.3474; */
-
-/* D93 (9300K) (a common monitor default, but poor colour reproduction) */
-/* static const double lxn = 0.2848; */
-/* static const double lyn = 0.2932; */
-
-/* illum E (normalized) */
-/*static const double lxn = 1.0/3.0; */
-/*static const double lyn = 1.0/3.0; */
-
-/* illum C (average sunlight) */
-/*static const double lxn = 0.3101; */
-/*static const double lyn = 0.3162; */
-
-/* illum B (direct sunlight) */
-/*static const double lxn = 0.3484; */
-/*static const double lyn = 0.3516; */
-
-/* illum A (tungsten lamp) */
-/*static const double lxn = 0.4476; */
-/*static const double lyn = 0.4074; */
-
-
-static const double LRAMP = 7.99959199;
-
-
-static double xnn, znn;
-
-
-typedef double CMatrix[3][3];
-typedef double CVector[3];
-
-static CMatrix Mrgb_to_xyz, Mxyz_to_rgb;
-
-static int
-Minvert (CMatrix src, CMatrix dest)
-{
- double det;
-
- dest[0][0] = src[1][1] * src[2][2] - src[1][2] * src[2][1];
- dest[0][1] = src[0][2] * src[2][1] - src[0][1] * src[2][2];
- dest[0][2] = src[0][1] * src[1][2] - src[0][2] * src[1][1];
- dest[1][0] = src[1][2] * src[2][0] - src[1][0] * src[2][2];
- dest[1][1] = src[0][0] * src[2][2] - src[0][2] * src[2][0];
- dest[1][2] = src[0][2] * src[1][0] - src[0][0] * src[1][2];
- dest[2][0] = src[1][0] * src[2][1] - src[1][1] * src[2][0];
- dest[2][1] = src[0][1] * src[2][0] - src[0][0] * src[2][1];
- dest[2][2] = src[0][0] * src[1][1] - src[0][1] * src[1][0];
-
- det =
- src[0][0] * dest[0][0] +
- src[0][1] * dest[1][0] +
- src[0][2] * dest[2][0];
-
- if (det <= 0.0)
- {
-#ifdef SANITY
- g_printerr ("\n\007 XXXX det: %f\n", det);
-#endif
- return 0;
- }
-
- dest[0][0] /= det;
- dest[0][1] /= det;
- dest[0][2] /= det;
- dest[1][0] /= det;
- dest[1][1] /= det;
- dest[1][2] /= det;
- dest[2][0] /= det;
- dest[2][1] /= det;
- dest[2][2] /= det;
-
- return 1;
-}
-
-
static void
rgbxyzrgb_init (void)
{
- /* The gamma related code has been removed since we do our
- * calculations in linear light. To revice that code, use version
- * control means
- */
-
- xnn = lxn / lyn;
- /* ynn taken as 1.0 */
- znn = (1.0 - (lxn + lyn)) / lyn;
-
- {
- CMatrix MRC, MRCi;
- double C1, C2, C3;
-
- MRC[0][0] = pxr;
- MRC[0][1] = pxg;
- MRC[0][2] = pxb;
- MRC[1][0] = pyr;
- MRC[1][1] = pyg;
- MRC[1][2] = pyb;
- MRC[2][0] = 1.0 - (pxr + pyr);
- MRC[2][1] = 1.0 - (pxg + pyg);
- MRC[2][2] = 1.0 - (pxb + pyb);
-
- Minvert (MRC, MRCi);
-
- C1 = MRCi[0][0] * xnn + MRCi[0][1] + MRCi[0][2] * znn;
- C2 = MRCi[1][0] * xnn + MRCi[1][1] + MRCi[1][2] * znn;
- C3 = MRCi[2][0] * xnn + MRCi[2][1] + MRCi[2][2] * znn;
-
- Mrgb_to_xyz[0][0] = MRC[0][0] * C1;
- Mrgb_to_xyz[0][1] = MRC[0][1] * C2;
- Mrgb_to_xyz[0][2] = MRC[0][2] * C3;
- Mrgb_to_xyz[1][0] = MRC[1][0] * C1;
- Mrgb_to_xyz[1][1] = MRC[1][1] * C2;
- Mrgb_to_xyz[1][2] = MRC[1][2] * C3;
- Mrgb_to_xyz[2][0] = MRC[2][0] * C1;
- Mrgb_to_xyz[2][1] = MRC[2][1] * C2;
- Mrgb_to_xyz[2][2] = MRC[2][2] * C3;
-
- Minvert (Mrgb_to_xyz, Mxyz_to_rgb);
- }
}
-
static void
-xyz_to_rgb (double *inx_outr,
- double *iny_outg,
- double *inz_outb)
+RGB_to_XYZ (double R,
+ double G,
+ double B,
+ double *to_X,
+ double *to_Y,
+ double *to_Z)
{
- const double x = *inx_outr;
- const double y = *iny_outg;
- const double z = *inz_outb;
- *inx_outr = Mxyz_to_rgb[0][0] * x + Mxyz_to_rgb[0][1] * y + Mxyz_to_rgb[0][2] * z;
- *iny_outg = Mxyz_to_rgb[1][0] * x + Mxyz_to_rgb[1][1] * y + Mxyz_to_rgb[1][2] * z;
- *inz_outb = Mxyz_to_rgb[2][0] * x + Mxyz_to_rgb[2][1] * y + Mxyz_to_rgb[2][2] * z;
-}
-
-
-static void
-rgb_to_xyz (double *inr_outx,
- double *ing_outy,
- double *inb_outz)
-{
- const double r = *inr_outx;
- const double g = *ing_outy;
- const double b = *inb_outz;
+ double RGBtoXYZ[3][3];
+
+/*
+ * The variables below hard-code the D50-adapted sRGB RGB to XYZ matrix.
+ *
+ * In a properly ICC profile color-managed application, this matrix
+ * is retrieved from the image's ICC profile's RGB colorants.
+ *
+ * */
+ RGBtoXYZ[0][0]= 0.43603516;
+ RGBtoXYZ[0][1]= 0.38511658;
+ RGBtoXYZ[0][2]= 0.14305115;
+ RGBtoXYZ[1][0]= 0.22248840;
+ RGBtoXYZ[1][1]= 0.71690369;
+ RGBtoXYZ[1][2]= 0.06060791;
+ RGBtoXYZ[2][0]= 0.01391602;
+ RGBtoXYZ[2][1]= 0.09706116;
+ RGBtoXYZ[2][2]= 0.71392822;
+
+/* Convert RGB to XYZ */
+ *to_X = RGBtoXYZ[0][0]*R + RGBtoXYZ[0][1]*G + RGBtoXYZ[0][2]*B;
+ *to_Y = RGBtoXYZ[1][0]*R + RGBtoXYZ[1][1]*G + RGBtoXYZ[1][2]*B;
+ *to_Z = RGBtoXYZ[2][0]*R + RGBtoXYZ[2][1]*G + RGBtoXYZ[2][2]*B;
- *inr_outx = Mrgb_to_xyz[0][0] * r + Mrgb_to_xyz[0][1] * g + Mrgb_to_xyz[0][2] * b;
- *ing_outy = Mrgb_to_xyz[1][0] * r + Mrgb_to_xyz[1][1] * g + Mrgb_to_xyz[1][2] * b;
- *inb_outz = Mrgb_to_xyz[2][0] * r + Mrgb_to_xyz[2][1] * g + Mrgb_to_xyz[2][2] * b;
}
-
-static inline double
-ffunc (const double t)
+static void XYZ_to_RGB (double X,
+ double Y,
+ double Z,
+ double *to_R,
+ double *to_G,
+ double *to_B)
{
- if (t > 0.008856)
- {
- return (cbrt (t));
- }
- else
- {
- return (7.787 * t + 16.0 / 116.0);
- }
-}
-
+ double XYZtoRGB[3][3];
+
+/*
+ * The variables below hard-code the inverse of
+ * the D50-adapted sRGB RGB to XYZ matrix.
+ *
+ * In a properly ICC profile color-managed application,
+ * this matrix is the inverse of the matrix
+ * retrieved from the image's ICC profile's RGB colorants.
+ *
+ * */
+ XYZtoRGB[0][0]= 3.134274799724;
+ XYZtoRGB[0][1]= -1.617275708956;
+ XYZtoRGB[0][2]= -0.490724283042;
+ XYZtoRGB[1][0]= -0.978795575994;
+ XYZtoRGB[1][1]= 1.916161689117;
+ XYZtoRGB[1][2]= 0.033453331711;
+ XYZtoRGB[2][0]= 0.071976988401;
+ XYZtoRGB[2][1]= -0.228984974402;
+ XYZtoRGB[2][2]= 1.405718224383;
+
+/* Convert XYZ to RGB */
+ *to_R = XYZtoRGB[0][0]*X + XYZtoRGB[0][1]*Y + XYZtoRGB[0][2]*Z;
+ *to_G = XYZtoRGB[1][0]*X + XYZtoRGB[1][1]*Y + XYZtoRGB[1][2]*Z;
+ *to_B = XYZtoRGB[2][0]*X + XYZtoRGB[2][1]*Y + XYZtoRGB[2][2]*Z;
-static inline double
-ffunc_inv (const double t)
-{
- if (t > 0.206893)
- {
- return (t * t * t);
- }
- else
- {
- return ((t - 16.0 / 116.0) / 7.787);
- }
}
-
static void
-xyz_to_lab (double *inx,
- double *iny,
- double *inz)
+XYZ_to_LAB (double X,
+ double Y,
+ double Z,
+ double *to_L,
+ double *to_a,
+ double *to_b
+ )
+
{
- double L, a, b;
- double ffuncY;
- const double X = *inx;
- const double Y = *iny;
- const double Z = *inz;
- if (Y > 0.0)
- {
- if (Y > 0.008856)
- {
- L = (116.0 * cbrt (Y)) - 16.0;
- }
- else
- {
- L = (Y * 903.3);
- }
-
-#ifdef SANITY
- if (L < 0.0)
- {
- g_printerr (" <eek1>%f \007", (float) L);
- }
-
- if (L > 100.0)
- {
- g_printerr (" <eek2>%f \007", (float) L);
- }
-#endif
- }
- else
- {
- L = 0.0;
- }
+ const double kappa = 903.3;//24389.0/27.0;
+ const double epsilon = 0.008856;//216/24389.0;
+
+/* The constants below hard-code the D50-adapted sRGB ICC profile
+ * reference white, aka the ICC profile D50 illuminant.
+ *
+ * In a properly ICC profile color-managed application, the profile
+ * illuminant values should be retrieved from the image's
+ * ICC profile's illuminant.
+ *
+ * At present, the ICC profile illuminant is always D50. This might
+ * change when the next version of the ICC specs is released.
+ *
+ * As encoded in an actual V2 or V4 ICC profile,
+ * the illuminant values are hexadecimal-rounded, as are the following
+ * hard-coded D50 ICC profile illuminant values:
+ *
+ * */
+ const double X_reference_white = 0.964202880;
+ const double Y_reference_white = 1.000000000;
+ const double Z_reference_white = 0.824905400;
+
+ double x_r = X/X_reference_white;
+ double y_r = Y/Y_reference_white;
+ double z_r = Z/Z_reference_white;
+
+ double f_x, f_y, f_z;
+
+ if (x_r > epsilon) f_x = pow(x_r, 1.0 / 3.0);
+ else ( f_x = ((kappa * x_r) + 16) / 116.0 );
+
+ if (y_r > epsilon) f_y = pow(y_r, 1.0 / 3.0);
+ else ( f_y = ((kappa * y_r) + 16) / 116.0 );
+
+ if (z_r > epsilon) f_z = pow(z_r, 1.0 / 3.0);
+ else ( f_z = ((kappa * z_r) + 16) / 116.0 );
+
+
+ *to_L = (116.0 * f_y) - 16.0;
+ *to_a = 500.0 * (f_x - f_y);
+ *to_b = 200.0 * (f_y - f_z);
- ffuncY = ffunc (Y);
- a = 500.0 * (ffunc (X / xnn) - ffuncY);
- b = 200.0 * (ffuncY - ffunc (Z / znn));
-
- *inx = L;
- *iny = a;
- *inz = b;
}
-
-static void
-lab_to_xyz (double *inl,
- double *ina,
- double *inb)
+static void LAB_to_XYZ (double L,
+ double a,
+ double b,
+ double *to_X,
+ double *to_Y,
+ double *to_Z)
{
- double X, Y, Z;
- double P;
- const double L = *inl;
- const double a = *ina;
- const double b = *inb;
-
- if (L > LRAMP)
- {
- P = Y = (L + 16.0) / 116.0;
- Y = Y * Y * Y;
- }
- else
- {
- Y = L / 903.3;
- P = 7.787 * Y + 16.0 / 116.0;
- }
- X = (P + a / 500.0);
- X = xnn *ffunc_inv (X);
- Z = (P - b / 200.0);
- Z = znn *ffunc_inv (Z);
+ const double kappa = 903.3;//24389.0/27.0;
+ const double epsilon = 0.008856;//216/24389.0;
+
+ double fy, fx, fz, fx_cubed, fy_cubed, fz_cubed;
+ double xr, yr, zr;
+
+/* The constants below hard-code the D50-adapted sRGB ICC profile
+ * reference white, aka the ICC profile D50 illuminant.
+ *
+ * In a properly ICC profile color-managed application, the profile
+ * illuminant values should be retrieved from the image's
+ * ICC profile's illuminant.
+ *
+ * At present, the ICC profile illuminant is always D50. This might
+ * change when the next version of the ICC specs is released.
+ *
+ * As encoded in an actual V2 or V4 ICC profile,
+ * the illuminant values are hexadecimal-rounded, as are the following
+ * hard-coded D50 ICC profile illuminant values:
+ *
+ * */
+ const double X_reference_white = 0.964202880;
+ const double Y_reference_white = 1.000000000;
+ const double Z_reference_white = 0.824905400;
+
+ fy = (L + 16.0) / 116.0;
+ fy_cubed = fy*fy*fy;
+
+ fz = fy - (b / 200.0);
+ fz_cubed = fz*fz*fz;
+
+ fx = (a / 500.0) + fy;
+ fx_cubed = fx*fx*fx;
+
+ if (fx_cubed > epsilon) xr = fx_cubed;
+ else xr = ((116.0 * fx) - 16) / kappa;
+
+ if ( L > (kappa * epsilon) ) yr = fy_cubed;
+ else yr = (L / kappa);
+
+ if (fz_cubed > epsilon) zr = fz_cubed;
+ else zr = ( (116.0 * fz) - 16 ) / kappa;
+
+ *to_X = xr * X_reference_white;
+ *to_Y = yr * Y_reference_white;
+ *to_Z = zr * Z_reference_white;
-#ifdef SANITY
- if (X < -0.00000)
- {
- if (X < -0.0001)
- g_printerr ("{badX %f {%f,%f,%f}}", X, L, a, b);
- X = 0.0;
- }
- if (Y < -0.00000)
- {
- if (Y < -0.0001)
- g_printerr ("{badY %f}", Y);
- Y = 0.0;
- }
- if (Z < -0.00000)
- {
- if (Z < -0.1)
- g_printerr ("{badZ %f}", Z);
- Z = 0.0;
- }
-#endif
-
- *inl = X;
- *ina = Y;
- *inb = Z;
}
-
-/* call this before using the CPercep function */
+/* Call this before using the RGB/CIE color space conversions */
static void
-cpercep_init (void)
+rgbcie_init (void)
{
static gboolean initialized = FALSE;
@@ -1202,161 +1069,4 @@ cpercep_init (void)
}
}
-static void
-cpercep_rgb_to_space (double inr,
- double ing,
- double inb,
- double *outr,
- double *outg,
- double *outb)
-{
-#ifdef APPROX
-#ifdef SANITY
- /* ADM extra sanity */
- if ((inr) > 255.0 ||
- (ing) > 255.0 ||
- (inb) > 255.0 ||
- (inr) < -0.0 ||
- (ing) < -0.0 ||
- (inb) < -0.0
- )
- abort ();
-#endif /* SANITY */
-#endif /* APPROX */
-
-#ifdef SANITY
- /* ADM extra sanity */
- if ((inr) > 1.0 ||
- (ing) > 1.0 ||
- (inb) > 1.0 ||
- (inr) < 0.0 ||
- (ing) < 0.0 ||
- (inb) < 0.0
- )
- {
- g_printerr ("%%");
- /* abort(); */
- }
-#endif /* SANITY */
-
- rgb_to_xyz (&inr, &ing, &inb);
-
-#ifdef SANITY
- if (inr < 0.0 || ing < 0.0 || inb < 0.0)
- {
- g_printerr (" [BAD2 XYZ: %f,%f,%f]\007 ",
- inr, ing, inb);
- }
-#endif /* SANITY */
-
- xyz_to_lab (&inr, &ing, &inb);
-
- *outr = inr;
- *outg = ing;
- *outb = inb;
-}
-
-
-static void
-cpercep_space_to_rgb (double inr,
- double ing,
- double inb,
- double *outr,
- double *outg,
- double *outb)
-{
- lab_to_xyz (&inr, &ing, &inb);
-
-#ifdef SANITY
- if (inr < -0.0 || ing < -0.0 || inb < -0.0)
- {
- g_printerr (" [BAD1 XYZ: %f,%f,%f]\007 ",
- inr, ing, inb);
- }
-#endif
-
- xyz_to_rgb (&inr, &ing, &inb);
-
- *outr = inr;
- *outg = ing;
- *outb = inb;
-}
-
-static void
-ab_to_chab (double a,
- double b,
- double *C,
- double *H)
-{
- *C = sqrt (a * a + b * b);
- *H = atan2 (b, a) * DEGREES_PER_RADIAN;
-
- /* Keep H within the range 0-360 */
- if (*H < 0.0)
- *H += 360;
-}
-
-static void
-chab_to_ab (double C,
- double H,
- double *a,
- double *b)
-{
- *a = cos (H * RADIANS_PER_DEGREE) * C;
- *b = sin (H * RADIANS_PER_DEGREE) * C;
-}
-
-
-#if 0
-/* EXPERIMENTAL SECTION */
-
-const double
-xscaler (const double start, const double end,
- const double me, const double him)
-{
- return start + ((end - start) * him) / (me + him);
-}
-
-
-void
-mix_colours (const double L1, const double a1, const double b1,
- const double L2, const double a2, const double b2,
- double *rtnL, double *rtna, double *rtnb,
- double mass1, double mass2)
-{
- double w1, w2;
-
-#if 0
- *rtnL = xscaler (L1, L2, mass1, mass2);
- *rtna = xscaler (a1, a2, mass1, mass2);
- *rtnb = xscaler (b1, b2, mass1, mass2);
-#else
-#if 1
- w1 = mass1 * L1;
- w2 = mass2 * L2;
-#else
- w1 = mass1 * (L1 * L1 * L1);
- w2 = mass2 * (L2 * L2 * L2);
-#endif
-
- *rtnL = xscaler (L1, L2, mass1, mass2);
-
- if (w1 <= 0.0 &&
- w2 <= 0.0)
- {
- *rtna =
- *rtnb = 0.0;
-#ifdef SANITY
- /* g_printerr ("\007OUCH. "); */
-#endif
- }
- else
- {
- *rtna = xscaler (a1, a2, w1, w2);
- *rtnb = xscaler (b1, b2, w1, w2);
- }
-#endif
-}
-#endif /* EXPERIMENTAL SECTION */
-
-/*********** /cpercep.c ********* */
+/*********** / RGB/CIE color space conversions ********* */
[
Date Prev][
Date Next] [
Thread Prev][
Thread Next]
[
Thread Index]
[
Date Index]
[
Author Index]
