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[sfnt] Improve sRGB constants. 

* src/base/ftbitmap.c (ft_gray_for_premultiplied_srgb_bgra): Use slightly
more precise values.

Fixes #1018.
This commit is contained in:
Tapish Ojha 2022-01-27 08:34:48 +01:00 committed by Werner Lemberg
parent 9476cb7eb3
commit 3d77756e73
1 changed files with 4 additions and 4 deletions
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8
src/base/ftbitmap.c
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@ -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.