Libav 0.7.1
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00001 /* 00002 * RLE encoder 00003 * Copyright (c) 2007 Bobby Bingham 00004 * 00005 * This file is part of Libav. 00006 * 00007 * Libav is free software; you can redistribute it and/or 00008 * modify it under the terms of the GNU Lesser General Public 00009 * License as published by the Free Software Foundation; either 00010 * version 2.1 of the License, or (at your option) any later version. 00011 * 00012 * Libav is distributed in the hope that it will be useful, 00013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00015 * Lesser General Public License for more details. 00016 * 00017 * You should have received a copy of the GNU Lesser General Public 00018 * License along with Libav; if not, write to the Free Software 00019 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00020 */ 00021 #include "avcodec.h" 00022 #include "rle.h" 00023 00033 static int count_pixels(const uint8_t *start, int len, int bpp, int same) 00034 { 00035 const uint8_t *pos; 00036 int count = 1; 00037 00038 for(pos = start + bpp; count < FFMIN(127, len); pos += bpp, count ++) { 00039 if(same != !memcmp(pos-bpp, pos, bpp)) { 00040 if(!same) { 00041 /* if bpp == 1, then 0 1 1 0 is more efficiently encoded as a single 00042 * raw block of pixels. for larger bpp, RLE is as good or better */ 00043 if(bpp == 1 && count + 1 < FFMIN(127, len) && *pos != *(pos+1)) 00044 continue; 00045 00046 /* if RLE can encode the next block better than as a raw block, 00047 * back up and leave _all_ the identical pixels for RLE */ 00048 count --; 00049 } 00050 break; 00051 } 00052 } 00053 00054 return count; 00055 } 00056 00057 int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr , int bpp, int w, 00058 int add_rep, int xor_rep, int add_raw, int xor_raw) 00059 { 00060 int count, x; 00061 uint8_t *out = outbuf; 00062 00063 for(x = 0; x < w; x += count) { 00064 /* see if we can encode the next set of pixels with RLE */ 00065 if((count = count_pixels(ptr, w-x, bpp, 1)) > 1) { 00066 if(out + bpp + 1 > outbuf + out_size) return -1; 00067 *out++ = (count ^ xor_rep) + add_rep; 00068 memcpy(out, ptr, bpp); 00069 out += bpp; 00070 } else { 00071 /* fall back on uncompressed */ 00072 count = count_pixels(ptr, w-x, bpp, 0); 00073 if(out + bpp*count >= outbuf + out_size) return -1; 00074 *out++ = (count ^ xor_raw) + add_raw; 00075 00076 memcpy(out, ptr, bpp * count); 00077 out += bpp * count; 00078 } 00079 00080 ptr += count * bpp; 00081 } 00082 00083 return out - outbuf; 00084 }