[babl] babl-space: babl_space_new_from_chromaticities add equalize_matrix argument

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 764f3218e90a44e3bbbdf155065175b19af6bc14
Author: Øyvind Kolås <pippin gimp org>
Date:   Sat Jun 9 19:11:26 2018 +0200

    babl-space: babl_space_new_from_chromaticities add equalize_matrix argument
    
    Part of the problem in issue #18
    
    This API is internal only for now so we can change it, changing to use a
    hard-coded pre-quantized chromaticities set for the internal sRGB space.
    
    This preserve the gray axis matrix equalization performed for other spaces used
    with babl, ideally we can improve the gray-axis equalization to match and
    return to using it also for sRGB.

 babl/babl-icc.c      |  2 +-
 babl/babl-internal.h |  3 ++-
 babl/babl-space.c    | 46 +++++++++++++++++++++++++++++-----------------
 3 files changed, 32 insertions(+), 19 deletions(-)
---
diff --git a/babl/babl-icc.c b/babl/babl-icc.c
index 2e934e4..e8393e3 100644
--- a/babl/babl-icc.c
+++ b/babl/babl-icc.c
@@ -889,7 +889,7 @@ babl_icc_make_space (const char   *icc_data,
                      red_x, red_y,
                      green_x, green_y,
                      blue_x, blue_y,
-                     trc_red, trc_green, trc_blue);
+                     trc_red, trc_green, trc_blue, 1);
        return ret;
      }
   }
diff --git a/babl/babl-internal.h b/babl/babl-internal.h
index 1a65fd3..150fabd 100644
--- a/babl/babl-internal.h
+++ b/babl/babl-internal.h
@@ -404,7 +404,8 @@ const Babl * babl_space_from_chromaticities (const char *name,
                                              double bx, double by,
                                              const Babl *trc_red,
                                              const Babl *trc_green,
-                                             const Babl *trc_blue);
+                                             const Babl *trc_blue,
+                                             int equalize_matrix);
 
 /**
  * babl_space_from_rgbxyz_matrix:
diff --git a/babl/babl-space.c b/babl/babl-space.c
index b5557fb..d601bb2 100644
--- a/babl/babl-space.c
+++ b/babl/babl-space.c
@@ -167,7 +167,7 @@ static void babl_matrix_equalize (double *in_mat)
   }
 }
 
-static void babl_space_compute_matrices (BablSpace *space)
+static void babl_space_compute_matrices (BablSpace *space, int equalize_matrix)
 {
 #define _ space->
   /* transform spaces xy(Y) specified data to XYZ */
@@ -196,7 +196,8 @@ static void babl_space_compute_matrices (BablSpace *space)
 
   babl_matrix_mul_matrix (chad, mat, mat);
 
-  babl_matrix_equalize (mat);
+  if (equalize_matrix)
+    babl_matrix_equalize (mat);
 
   memcpy (space->RGBtoXYZ, mat, sizeof (mat));
 
@@ -298,7 +299,6 @@ babl_space_from_rgbxyz_matrix (const char *name,
   return (Babl*)&space_db[i];
 }
 
-
 const Babl *
 babl_space_from_chromaticities (const char *name,
                                 double wx, double wy,
@@ -307,7 +307,8 @@ babl_space_from_chromaticities (const char *name,
                                 double bx, double by,
                                 const Babl *trc_red,
                                 const Babl *trc_green,
-                                const Babl *trc_blue)
+                                const Babl *trc_blue,
+                                int equalize_matrix)
 {
   int i=0;
   static BablSpace space;
@@ -357,7 +358,7 @@ babl_space_from_chromaticities (const char *name,
              babl_get_name(space.trc[1]), babl_get_name(space.trc[2]));
 
   /* compute matrixes */
-  babl_space_compute_matrices (&space_db[i]);
+  babl_space_compute_matrices (&space_db[i], equalize_matrix);
 
   return (Babl*)&space_db[i];
 }
@@ -375,12 +376,23 @@ babl_space_class_for_each (BablEachFunction each_fun,
 void
 babl_space_class_init (void)
 {
+#if 0
   babl_space_from_chromaticities ("sRGB",
                0.3127,  0.3290, /* D65 */
                0.6400,  0.3300,
                0.3000,  0.6000,
                0.1500,  0.0600,
-               babl_trc("sRGB"), NULL, NULL);
+               babl_trc("sRGB"), NULL, NULL, 1);
+#else
+  babl_space_from_chromaticities ("sRGB",
+                0.3127,  0.3290, /* D65 */
+                0.639998686, 0.330010138,
+                0.300003784, 0.600003357,
+                0.150002046, 0.059997204,
+                babl_trc("sRGB"), NULL, NULL,
+                0);
+  /* hard-coded pre-quantized values - to match exactly what is used in standards see issue #18 */
+#endif
 
   babl_space_from_chromaticities ("Rec2020",
                0.3127,  0.3290, /* D65 */
@@ -388,7 +400,7 @@ babl_space_class_init (void)
                0.170,  0.797,
                0.131,  0.046,
                // XXX: is using sRGB TRC right?
-               babl_trc("sRGB"), NULL, NULL);
+               babl_trc("sRGB"), NULL, NULL, 1);
 
   babl_space_from_chromaticities (
       "Adobish",  /* a space that can be used as a place-holder for a sRGB like
@@ -400,7 +412,7 @@ computations of uniform gray axis */
       0.6400,  0.3300,
       0.2100,  0.7100,
       0.1500,  0.0600,
-      babl_trc("2.2"), NULL, NULL);
+      babl_trc("2.2"), NULL, NULL, 1);
 
   babl_space_from_chromaticities (
       "ProPhoto",
@@ -408,7 +420,7 @@ computations of uniform gray axis */
       0.7347,  0.2653,
       0.1596,  0.8404,
       0.0366,  0.0001,
-      babl_trc("1.8"), NULL, NULL);
+      babl_trc("1.8"), NULL, NULL, 1);
 
   babl_space_from_chromaticities (
       "Apple",
@@ -416,7 +428,7 @@ computations of uniform gray axis */
       0.6250,  0.3400,
       0.2800,  0.5950,
       0.1550,  0.0700,
-      babl_trc("1.8"), NULL, NULL);
+      babl_trc("1.8"), NULL, NULL, 1);
 
 #if 0
   babl_space_from_chromaticities (
@@ -425,7 +437,7 @@ computations of uniform gray axis */
      0.7350,  0.2650,
      0.1150,  0.8260,
      0.1570,  0.0180,
-     babl_trc("2.2"), NULL, NULL);
+     babl_trc("2.2"), NULL, NULL, 1);
 
   babl_space_from_chromaticities (
       "Best",
@@ -433,7 +445,7 @@ computations of uniform gray axis */
       0.7347,  0.2653,
       0.2150,  0.7750,
       0.1300,  0.0350,
-      babl_trc("2.2"), NULL, NULL);
+      babl_trc("2.2"), NULL, NULL, 1);
 
   babl_space_from_chromaticities (
       "Beta",
@@ -441,7 +453,7 @@ computations of uniform gray axis */
       0.6888,  0.3112,
       0.1986,  0.7551,
       0.1265,  0.0352,
-      babl_trc("2.2"), NULL, NULL);
+      babl_trc("2.2"), NULL, NULL, 1);
 
   babl_space_from_chromaticities (
       "Bruce",
@@ -457,7 +469,7 @@ computations of uniform gray axis */
       0.6400,  0.3300,
       0.2900,  0.6000,
       0.1500,  0.0600,
-      babl_trc("2.2"), NULL, NULL);
+      babl_trc("2.2"), NULL, NULL, 1);
 
   babl_space_from_chromaticities (
       "SMPTE-C",
@@ -465,7 +477,7 @@ computations of uniform gray axis */
       0.6300,  0.3300,
       0.3100,  0.5950,
       0.1550,  0.0700,
-      babl_trc("2.2"), NULL, NULL);
+      babl_trc("2.2"), NULL, NULL, 1);
 
   babl_space_from_chromaticities (
       "ColorMatch",
@@ -473,7 +485,7 @@ computations of uniform gray axis */
       0.6300,  0.3400,
       0.2950,  0.6050,
       0.1500,  0.0750,
-      babl_trc("1.8"), NULL, NULL);
+      babl_trc("1.8"), NULL, NULL, 1);
 
   babl_space_from_chromaticities (
      "Don RGB 4",
@@ -481,7 +493,7 @@ computations of uniform gray axis */
      0.6960,  0.3000,
      0.2150,  0.7650,
      0.1300,  0.0350,
-     babl_trc("1.8"), NULL, NULL);
+     babl_trc("1.8"), NULL, NULL, 1);
 #endif
 }