FFmpeg: libavcodec/s3tc.c Source File

00001 /*
00002  * S3 Texture Compression (S3TC) decoding functions
00003  * Copyright (c) 2007 by Ivo van Poorten
00004  *
00005  * see also: http://wiki.multimedia.cx/index.php?title=S3TC
00006  *
00007  * This file is part of FFmpeg.
00008  *
00009  * FFmpeg is free software; you can redistribute it and/or
00010  * modify it under the terms of the GNU Lesser General Public
00011  * License as published by the Free Software Foundation; either
00012  * version 2.1 of the License, or (at your option) any later version.
00013  *
00014  * FFmpeg is distributed in the hope that it will be useful,
00015  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00016  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00017  * Lesser General Public License for more details.
00018  *
00019  * You should have received a copy of the GNU Lesser General Public
00020  * License along with FFmpeg; if not, write to the Free Software
00021  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00022  */
00023 
00024 #include "libavcodec/bytestream.h"
00025 #include "avcodec.h"
00026 #include "s3tc.h"
00027 
00028 static inline void dxt1_decode_pixels(GetByteContext *gb, uint32_t *d,
00029                                       unsigned int qstride, unsigned int flag,
00030                                       uint64_t alpha) {
00031     unsigned int x, y, c0, c1, a = (!flag * 255u) << 24;
00032     unsigned int rb0, rb1, rb2, rb3, g0, g1, g2, g3;
00033     uint32_t colors[4], pixels;
00034 
00035     c0 = bytestream2_get_le16(gb);
00036     c1 = bytestream2_get_le16(gb);
00037 
00038     rb0  = (c0<<3 | c0<<8) & 0xf800f8;
00039     rb1  = (c1<<3 | c1<<8) & 0xf800f8;
00040     rb0 +=        (rb0>>5) & 0x070007;
00041     rb1 +=        (rb1>>5) & 0x070007;
00042     g0   =        (c0 <<5) & 0x00fc00;
00043     g1   =        (c1 <<5) & 0x00fc00;
00044     g0  +=        (g0 >>6) & 0x000300;
00045     g1  +=        (g1 >>6) & 0x000300;
00046 
00047     colors[0] = rb0 + g0 + a;
00048     colors[1] = rb1 + g1 + a;
00049 
00050     if (c0 > c1 || flag) {
00051         rb2 = (((2*rb0+rb1) * 21) >> 6) & 0xff00ff;
00052         rb3 = (((2*rb1+rb0) * 21) >> 6) & 0xff00ff;
00053         g2  = (((2*g0 +g1 ) * 21) >> 6) & 0x00ff00;
00054         g3  = (((2*g1 +g0 ) * 21) >> 6) & 0x00ff00;
00055         colors[3] = rb3 + g3 + a;
00056     } else {
00057         rb2 = ((rb0+rb1) >> 1) & 0xff00ff;
00058         g2  = ((g0 +g1 ) >> 1) & 0x00ff00;
00059         colors[3] = 0;
00060     }
00061 
00062     colors[2] = rb2 + g2 + a;
00063 
00064     pixels = bytestream2_get_le32(gb);
00065     for (y=0; y<4; y++) {
00066         for (x=0; x<4; x++) {
00067             a        = (alpha & 0x0f) << 28;
00068             a       += a >> 4;
00069             d[x]     = a + colors[pixels&3];
00070             pixels >>= 2;
00071             alpha  >>= 4;
00072         }
00073         d += qstride;
00074     }
00075 }
00076 
00077 void ff_decode_dxt1(GetByteContext *gb, uint8_t *dst,
00078                     const unsigned int w, const unsigned int h,
00079                     const unsigned int stride) {
00080     unsigned int bx, by, qstride = stride/4;
00081     uint32_t *d = (uint32_t *) dst;
00082 
00083     for (by=0; by < h/4; by++, d += stride-w)
00084         for (bx = 0; bx < w / 4; bx++, d += 4)
00085             dxt1_decode_pixels(gb, d, qstride, 0, 0LL);
00086 }
00087 
00088 void ff_decode_dxt3(GetByteContext *gb, uint8_t *dst,
00089                     const unsigned int w, const unsigned int h,
00090                     const unsigned int stride) {
00091     unsigned int bx, by, qstride = stride/4;
00092     uint32_t *d = (uint32_t *) dst;
00093 
00094     for (by=0; by < h/4; by++, d += stride-w)
00095         for (bx = 0; bx < w / 4; bx++, d += 4)
00096             dxt1_decode_pixels(gb, d, qstride, 1, bytestream2_get_le64(gb));
00097 }