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stb_image: Fix rounding during unpremultiply. 

This is the same method as in pull request #455, but using integer
arithmetic instead of converting to float.

Fixes #455.
dev
Fabian Giesen 2017-07-22 15:59:41 -07:00
parent 463dd85f1f
commit 25a2596b2f
1 changed files with 5 additions and 4 deletions
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9
stb_image.h
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@ -98,7 +98,7 @@ RECENT REVISION HISTORY:
Michaelangel007@github Philipp Wiesemann Dale Weiler github:grim210
Oriol Ferrer Mesia Josh Tobin Matthew Gregan github:sammyhw
Blazej Dariusz Roszkowski Gregory Mullen github:phprus
Kevin Schmidt github:poppolopoppo
Christian Floisand Kevin Schmidt github:poppolopoppo
*/
#ifndef STBI_INCLUDE_STB_IMAGE_H
@ -4670,9 +4670,10 @@ static void stbi__de_iphone(stbi__png *z)
stbi_uc a = p[3];
stbi_uc t = p[0];
if (a) {
p[0] = p[2] * 255 / a;
p[1] = p[1] * 255 / a;
p[2] = t * 255 / a;
stbi_uc half = a / 2;
p[0] = (p[2] * 255 + half) / a;
p[1] = (p[1] * 255 + half) / a;
p[2] = ( t * 255 + half) / a;
} else {
p[0] = p[2];
p[2] = t;