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/*
* S3 Texture Compression (S3TC) decoding functions
* Copyright (c) 2007 by Ivo van Poorten
*
* see also: http://wiki.multimedia.cx/index.php?title=S3TC
*
* This file is part of FFmpeg.
*
* FFmpeg 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.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavcodec/bytestream.h"
#include "avcodec.h"
#include "s3tc.h"
static inline void dxt1_decode_pixels(GetByteContext *gb, uint32_t *d,
unsigned int qstride, unsigned int flag,
uint64_t alpha) {
unsigned int x, y, c0, c1, a = (!flag * 255u) << 24;
unsigned int rb0, rb1, rb2, rb3, g0, g1, g2, g3;
uint32_t colors[4], pixels;
c0 = bytestream2_get_le16(gb);
c1 = bytestream2_get_le16(gb);
rb0 = (c0<<3 | c0<<8) & 0xf800f8;
rb1 = (c1<<3 | c1<<8) & 0xf800f8;
rb0 += (rb0>>5) & 0x070007;
rb1 += (rb1>>5) & 0x070007;
g0 = (c0 <<5) & 0x00fc00;
g1 = (c1 <<5) & 0x00fc00;
g0 += (g0 >>6) & 0x000300;
g1 += (g1 >>6) & 0x000300;
colors[0] = rb0 + g0 + a;
colors[1] = rb1 + g1 + a;
if (c0 > c1 || flag) {
rb2 = (((2*rb0+rb1) * 21) >> 6) & 0xff00ff;
rb3 = (((2*rb1+rb0) * 21) >> 6) & 0xff00ff;
g2 = (((2*g0 +g1 ) * 21) >> 6) & 0x00ff00;
g3 = (((2*g1 +g0 ) * 21) >> 6) & 0x00ff00;
colors[3] = rb3 + g3 + a;
} else {
rb2 = ((rb0+rb1) >> 1) & 0xff00ff;
g2 = ((g0 +g1 ) >> 1) & 0x00ff00;
colors[3] = 0;
}
colors[2] = rb2 + g2 + a;
pixels = bytestream2_get_le32(gb);
for (y=0; y<4; y++) {
for (x=0; x<4; x++) {
a = (alpha & 0x0f) << 28;
a += a >> 4;
d[x] = a + colors[pixels&3];
pixels >>= 2;
alpha >>= 4;
}
d += qstride;
}
}
void ff_decode_dxt1(GetByteContext *gb, uint8_t *dst,
const unsigned int w, const unsigned int h,
const unsigned int stride) {
unsigned int bx, by, qstride = stride/4;
uint32_t *d = (uint32_t *) dst;
for (by=0; by < h/4; by++, d += stride-w)
for (bx = 0; bx < w / 4; bx++, d += 4)
dxt1_decode_pixels(gb, d, qstride, 0, 0LL);
}
void ff_decode_dxt3(GetByteContext *gb, uint8_t *dst,
const unsigned int w, const unsigned int h,
const unsigned int stride) {
unsigned int bx, by, qstride = stride/4;
uint32_t *d = (uint32_t *) dst;
for (by=0; by < h/4; by++, d += stride-w)
for (bx = 0; bx < w / 4; bx++, d += 4)
dxt1_decode_pixels(gb, d, qstride, 1, bytestream2_get_le64(gb));
}
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