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98 lines
3.2 KiB
C
98 lines
3.2 KiB
C
/*
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* S3 Texture Compression (S3TC) decoding functions
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* Copyright (c) 2007 by Ivo van Poorten
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*
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* see also: http://wiki.multimedia.cx/index.php?title=S3TC
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "libavutil/intreadwrite.h"
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#include "avcodec.h"
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#include "s3tc.h"
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static inline void dxt1_decode_pixels(const uint8_t *s, uint32_t *d,
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unsigned int qstride, unsigned int flag,
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uint64_t alpha) {
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unsigned int x, y, c0, c1, a = (!flag * 255u) << 24;
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unsigned int rb0, rb1, rb2, rb3, g0, g1, g2, g3;
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uint32_t colors[4], pixels;
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c0 = AV_RL16(s);
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c1 = AV_RL16(s+2);
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rb0 = (c0<<3 | c0<<8) & 0xf800f8;
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rb1 = (c1<<3 | c1<<8) & 0xf800f8;
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rb0 += (rb0>>5) & 0x070007;
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rb1 += (rb1>>5) & 0x070007;
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g0 = (c0 <<5) & 0x00fc00;
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g1 = (c1 <<5) & 0x00fc00;
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g0 += (g0 >>6) & 0x000300;
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g1 += (g1 >>6) & 0x000300;
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colors[0] = rb0 + g0 + a;
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colors[1] = rb1 + g1 + a;
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if (c0 > c1 || flag) {
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rb2 = (((2*rb0+rb1) * 21) >> 6) & 0xff00ff;
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rb3 = (((2*rb1+rb0) * 21) >> 6) & 0xff00ff;
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g2 = (((2*g0 +g1 ) * 21) >> 6) & 0x00ff00;
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g3 = (((2*g1 +g0 ) * 21) >> 6) & 0x00ff00;
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colors[3] = rb3 + g3 + a;
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} else {
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rb2 = ((rb0+rb1) >> 1) & 0xff00ff;
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g2 = ((g0 +g1 ) >> 1) & 0x00ff00;
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colors[3] = 0;
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}
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colors[2] = rb2 + g2 + a;
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pixels = AV_RL32(s+4);
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for (y=0; y<4; y++) {
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for (x=0; x<4; x++) {
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a = (alpha & 0x0f) << 28;
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a += a >> 4;
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d[x] = a + colors[pixels&3];
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pixels >>= 2;
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alpha >>= 4;
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}
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d += qstride;
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}
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}
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void ff_decode_dxt1(const uint8_t *s, uint8_t *dst,
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const unsigned int w, const unsigned int h,
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const unsigned int stride) {
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unsigned int bx, by, qstride = stride/4;
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uint32_t *d = (uint32_t *) dst;
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for (by=0; by < h/4; by++, d += stride-w)
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for (bx=0; bx < w/4; bx++, s+=8, d+=4)
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dxt1_decode_pixels(s, d, qstride, 0, 0LL);
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}
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void ff_decode_dxt3(const uint8_t *s, uint8_t *dst,
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const unsigned int w, const unsigned int h,
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const unsigned int stride) {
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unsigned int bx, by, qstride = stride/4;
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uint32_t *d = (uint32_t *) dst;
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for (by=0; by < h/4; by++, d += stride-w)
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for (bx=0; bx < w/4; bx++, s+=16, d+=4)
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dxt1_decode_pixels(s+8, d, qstride, 1, AV_RL64(s));
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}
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