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SDL_alphamult.c
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/*
SDL - Simple DirectMedia Layer
Copyright (C) 1997-2009 Sam Lantinga
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Sam Lantinga
slouken@libsdl.org
*/
#include "SDL_config.h"
#include "SDL_blit.h"
#include "SDL_alphamult.h"
/* Functions to pre-multiply the alpha channel into the color channels */
#define DEFINE_PREMULTIPLY_FUNC(fmt) \
void \
SDL_PreMultiplyAlpha##fmt(int w, int h, Uint32 *pixels, int pitch) \
{ \
pitch /= 4; \
while (h--) { \
int n; \
Uint32 *row = pixels; \
Uint32 pixel; \
unsigned r, g, b, a; \
\
for (n = w; n--; ) { \
pixel = *row; \
RGBA_FROM_##fmt(pixel, r, g, b, a); \
r = (r * a) / 255; \
g = (g * a) / 255; \
b = (b * a) / 255; \
fmt##_FROM_RGBA(*row, r, g, b, a); \
++row; \
} \
pixels += pitch; \
} \
}
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/* *INDENT-OFF* */
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DEFINE_PREMULTIPLY_FUNC(ARGB8888)
DEFINE_PREMULTIPLY_FUNC(RGBA8888)
DEFINE_PREMULTIPLY_FUNC(ABGR8888)
DEFINE_PREMULTIPLY_FUNC(BGRA8888)
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/* *INDENT-ON* */
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/* vi: set ts=4 sw=4 expandtab: */