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[base] Clean up bitmap conversion.

* src/base/ftbitmap.c (ft_gray_for_premultiplied_srgb_bgra): Use
appropriate FT_DivFix and remove superfluous upscaling.

git/fs: mount .git/fs: mount/attach disallowed

--- a/ChangeLog

+++ b/ChangeLog

@@ -1,3 +1,10 @@

+2014-07-11  Alexei Podtelezhnikov  <[email protected]>

+

+	[base] Clean up bitmap conversion.

+

+	* src/base/ftbitmap.c (ft_gray_for_premultiplied_srgb_bgra): Use

+	appropriate FT_DivFix and remove superfluous upscaling.

+

 2014-07-04  Alexei Podtelezhnikov  <[email protected]>

 	[base] Small optimization of the ancient code.

--- a/src/base/ftbitmap.c

+++ b/src/base/ftbitmap.c

@@ -401,10 +401,9 @@

      */

     /* Undo premultification, get the number in a 16.16 form. */

-    b = FT_MulDiv( b, 65536, a );

-    g = FT_MulDiv( g, 65536, a );

-    r = FT_MulDiv( r, 65536, a );

-    a = a * 256;

+    b = FT_DivFix( b, a );

+    g = FT_DivFix( g, a );

+    r = FT_DivFix( r, a );

     /* Apply gamma of 2.0 instead of 2.2. */

     b = FT_MulFix( b, b );

@@ -425,10 +424,10 @@

      * - If alpha is zero and luminosity is zero, we want 255.

      * - If alpha is zero and luminosity is one, we want 0.

      *

-     * So the formula is a * (1 - l).

+     * So the formula is a * (1 - l) = a - l * a.

      */

-    return (FT_Byte)( FT_MulFix( 65535 - l, a ) >> 8 );

+    return a - (FT_Byte)FT_MulFix( l, a );

   }