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[libpng15] Multiple transform bug fixes plus a work-round for double gamma

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correction.
This commit is contained in:
John Bowler
2011-11-16 14:26:34 -06:00
committed by Glenn Randers-Pehrson
parent 36f5884359
commit 18c5cfafeb
5 changed files with 477 additions and 45 deletions
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16
pngwrite.c
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@@ -1878,7 +1878,7 @@ png_write_image_8bit(png_voidp argument)
/* Need 32 bit accuracy in the sRGB tables */
png_uint_32 component = *in_ptr++;
/* The following gives 65535 for an alpha of 0, which is fine,
/* The following gives 1.0 for an alpha of 0, which is fine,
* otherwise if 0/0 is represented as some other value there is
* more likely to be a discontinuity which will probably damage
* compression when moving from a fully transparent area to a
@@ -1891,11 +1891,17 @@ png_write_image_8bit(png_voidp argument)
/* component<alpha, so component/alpha is less than one and
* component*reciprocal is less than 2^31.
*/
else if (component > 0 && alpha < 65535)
else if (component > 0)
{
component *= reciprocal;
component += 64; /* round to nearest */
component >>= 7;
if (alpha < 65535)
{
component *= reciprocal;
component += 64; /* round to nearest */
component >>= 7;
}
else
component *= 255;
/* Convert the component to sRGB. */
*out_ptr++ = (png_byte)PNG_sRGB_FROM_LINEAR(component);