1/* 2 * S3 Texture Compression (S3TC) decoding functions 3 * Copyright (c) 2007 by Ivo van Poorten 4 * 5 * see also: http://wiki.multimedia.cx/index.php?title=S3TC 6 * 7 * This file is part of FFmpeg. 8 * 9 * FFmpeg is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU Lesser General Public 11 * License as published by the Free Software Foundation; either 12 * version 2.1 of the License, or (at your option) any later version. 13 * 14 * FFmpeg is distributed in the hope that it will be useful, 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 17 * Lesser General Public License for more details. 18 * 19 * You should have received a copy of the GNU Lesser General Public 20 * License along with FFmpeg; if not, write to the Free Software 21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 22 */ 23 24#include "libavutil/intreadwrite.h" 25#include "avcodec.h" 26#include "s3tc.h" 27 28static inline void dxt1_decode_pixels(const uint8_t *s, uint32_t *d, 29 unsigned int qstride, unsigned int flag, 30 uint64_t alpha) { 31 unsigned int x, y, c0, c1, a = (!flag * 255) << 24; 32 unsigned int rb0, rb1, rb2, rb3, g0, g1, g2, g3; 33 uint32_t colors[4], pixels; 34 35 c0 = AV_RL16(s); 36 c1 = AV_RL16(s+2); 37 38 rb0 = (c0<<3 | c0<<8) & 0xf800f8; 39 rb1 = (c1<<3 | c1<<8) & 0xf800f8; 40 rb0 += (rb0>>5) & 0x070007; 41 rb1 += (rb1>>5) & 0x070007; 42 g0 = (c0 <<5) & 0x00fc00; 43 g1 = (c1 <<5) & 0x00fc00; 44 g0 += (g0 >>6) & 0x000300; 45 g1 += (g1 >>6) & 0x000300; 46 47 colors[0] = rb0 + g0 + a; 48 colors[1] = rb1 + g1 + a; 49 50 if (c0 > c1 || flag) { 51 rb2 = (((2*rb0+rb1) * 21) >> 6) & 0xff00ff; 52 rb3 = (((2*rb1+rb0) * 21) >> 6) & 0xff00ff; 53 g2 = (((2*g0 +g1 ) * 21) >> 6) & 0x00ff00; 54 g3 = (((2*g1 +g0 ) * 21) >> 6) & 0x00ff00; 55 colors[3] = rb3 + g3 + a; 56 } else { 57 rb2 = ((rb0+rb1) >> 1) & 0xff00ff; 58 g2 = ((g0 +g1 ) >> 1) & 0x00ff00; 59 colors[3] = 0; 60 } 61 62 colors[2] = rb2 + g2 + a; 63 64 pixels = AV_RL32(s+4); 65 for (y=0; y<4; y++) { 66 for (x=0; x<4; x++) { 67 a = (alpha & 0x0f) << 28; 68 a += a >> 4; 69 d[x] = a + colors[pixels&3]; 70 pixels >>= 2; 71 alpha >>= 4; 72 } 73 d += qstride; 74 } 75} 76 77void ff_decode_dxt1(const uint8_t *s, uint8_t *dst, 78 const unsigned int w, const unsigned int h, 79 const unsigned int stride) { 80 unsigned int bx, by, qstride = stride/4; 81 uint32_t *d = (uint32_t *) dst; 82 83 for (by=0; by < h/4; by++, d += stride-w) 84 for (bx=0; bx < w/4; bx++, s+=8, d+=4) 85 dxt1_decode_pixels(s, d, qstride, 0, 0LL); 86} 87 88void ff_decode_dxt3(const uint8_t *s, uint8_t *dst, 89 const unsigned int w, const unsigned int h, 90 const unsigned int stride) { 91 unsigned int bx, by, qstride = stride/4; 92 uint32_t *d = (uint32_t *) dst; 93 94 for (by=0; by < h/4; by++, d += stride-w) 95 for (bx=0; bx < w/4; bx++, s+=16, d+=4) 96 dxt1_decode_pixels(s+8, d, qstride, 1, AV_RL64(s)); 97} 98