[Git][freetype/freetype][master] [sfnt] Improve sRGB constants.

[Werner Lemberg (@wl)]

Werner Lemberg pushed to branch master at FreeType / FreeType

Commits:

• 3d77756e
  by Tapish Ojha at 2022-01-27T08:43:19+01:00

  [sfnt] Improve sRGB constants.
  
  * src/base/ftbitmap.c (ft_gray_for_premultiplied_srgb_bgra): Use slightly
  more precise values.
  
  Fixes #1018.
  

1 changed file:

• src/base/ftbitmap.c

Changes:

src/base/ftbitmap.c

---

...	...	@@ -480,7 +480,7 @@
480	480	* A gamma of 2.2 is fair to assume. And then, we need to
481	481	* undo the premultiplication too.
482	482	*
483		- * https://accessibility.kde.org/hsl-adjusted.php
	483	+ * http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html#SideNotes
484	484	*
485	485	* We do the computation with integers only, applying a gamma of 2.0.
486	486	* We guarantee 32-bit arithmetic to avoid overflow but the resulting
...	...	@@ -488,9 +488,9 @@
488	488	*
489	489	*/
490	490
491		- l = ( 4732UL /* 0.0722 * 65536 */ * bgra[0] * bgra[0] +
492		- 46871UL /* 0.7152 * 65536 */ * bgra[1] * bgra[1] +
493		- 13933UL /* 0.2126 * 65536 */ * bgra[2] * bgra[2] ) >> 16;
	491	+ l = ( 4731UL /* 0.072186 * 65536 */ * bgra[0] * bgra[0] +
	492	+ 46868UL /* 0.715158 * 65536 */ * bgra[1] * bgra[1] +
	493	+ 13937UL /* 0.212656 * 65536 */ * bgra[2] * bgra[2] ) >> 16;
494	494
495	495	/*
496	496	* Final transparency can be determined as follows.

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