[sfnt] Improve sRGB constants.
* src/base/ftbitmap.c (ft_gray_for_premultiplied_srgb_bgra): Use slightly
more precise values.
Fixes #1018.
diff --git a/src/base/ftbitmap.c b/src/base/ftbitmap.c
index 8a419c2..7825895 100644
--- a/src/base/ftbitmap.c
+++ b/src/base/ftbitmap.c
@@ -480,7 +480,7 @@
* A gamma of 2.2 is fair to assume. And then, we need to
* undo the premultiplication too.
*
- * https://accessibility.kde.org/hsl-adjusted.php
+ * http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html#SideNotes
*
* We do the computation with integers only, applying a gamma of 2.0.
* We guarantee 32-bit arithmetic to avoid overflow but the resulting
@@ -488,9 +488,9 @@
*
*/
- l = ( 4732UL /* 0.0722 * 65536 */ * bgra[0] * bgra[0] +
- 46871UL /* 0.7152 * 65536 */ * bgra[1] * bgra[1] +
- 13933UL /* 0.2126 * 65536 */ * bgra[2] * bgra[2] ) >> 16;
+ l = ( 4731UL /* 0.072186 * 65536 */ * bgra[0] * bgra[0] +
+ 46868UL /* 0.715158 * 65536 */ * bgra[1] * bgra[1] +
+ 13937UL /* 0.212656 * 65536 */ * bgra[2] * bgra[2] ) >> 16;
/*
* Final transparency can be determined as follows.
