[gimp] libgimpcolor: change LUMINANCE Y values to match sRGB built-in profile

[Michael Natterer <mitch src gnome org>]

commit 3925466db5c076dc608eb1a708642040189e2414
Author: Elle Stone <ellestone ninedegreesbelow com>
Date:   Sat Feb 7 12:20:36 2015 -0500

    libgimpcolor: change LUMINANCE Y values to match sRGB built-in profile

 libgimpcolor/gimprgb.h |   16 ++++++++--------
 1 files changed, 8 insertions(+), 8 deletions(-)
---
diff --git a/libgimpcolor/gimprgb.h b/libgimpcolor/gimprgb.h
index d5ece7e..52f0f0b 100644
--- a/libgimpcolor/gimprgb.h
+++ b/libgimpcolor/gimprgb.h
@@ -179,19 +179,19 @@ gdouble   gimp_rgba_distance       (const GimpRGB *rgba1,
 
 
 
-/*  Map RGB to intensity  */
+/*  Map D50-adapted sRGB to luminance  */
 
 /*
  * The weights to compute true CIE luminance from linear red, green
- * and blue, as defined by the ITU-R Recommendation BT.709, "Basic
- * Parameter Values for the HDTV Standard for the Studio and for
- * International Programme Exchange" (1990). Also suggested in the
- * sRGB colorspace specification by the W3C.
+ * and blue as defined by the sRGB color space specs in an ICC profile
+ * color managed application. The weights below have been chromatically
+ * adapted from D65 (as specified by the sRGB color space specs)
+ * to D50 (as specified by D50 illuminant values in the ICC V4 specs).
  */
 
-#define GIMP_RGB_LUMINANCE_RED    (0.2126)
-#define GIMP_RGB_LUMINANCE_GREEN  (0.7152)
-#define GIMP_RGB_LUMINANCE_BLUE   (0.0722)
+#define GIMP_RGB_LUMINANCE_RED    (0.22248840)
+#define GIMP_RGB_LUMINANCE_GREEN  (0.71690369)
+#define GIMP_RGB_LUMINANCE_BLUE   (0.06060791)
 
 #define GIMP_RGB_LUMINANCE(r,g,b) ((r) * GIMP_RGB_LUMINANCE_RED   + \
                                    (g) * GIMP_RGB_LUMINANCE_GREEN + \