1/* 2 * RLE encoder 3 * Copyright (c) 2007 Bobby Bingham 4 * 5 * This file is part of FFmpeg. 6 * 7 * FFmpeg is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * FFmpeg is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with FFmpeg; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21#include "avcodec.h" 22#include "rle.h" 23 24/** 25 * Count up to 127 consecutive pixels which are either all the same or 26 * all differ from the previous and next pixels. 27 * @param start Pointer to the first pixel 28 * @param len Maximum number of pixels 29 * @param bpp Bytes per pixel 30 * @param same 1 if searching for identical pixel values. 0 for differing 31 * @return Number of matching consecutive pixels found 32 */ 33static int count_pixels(const uint8_t *start, int len, int bpp, int same) 34{ 35 const uint8_t *pos; 36 int count = 1; 37 38 for(pos = start + bpp; count < FFMIN(127, len); pos += bpp, count ++) { 39 if(same != !memcmp(pos-bpp, pos, bpp)) { 40 if(!same) { 41 /* if bpp == 1, then 0 1 1 0 is more efficiently encoded as a single 42 * raw block of pixels. for larger bpp, RLE is as good or better */ 43 if(bpp == 1 && count + 1 < FFMIN(127, len) && *pos != *(pos+1)) 44 continue; 45 46 /* if RLE can encode the next block better than as a raw block, 47 * back up and leave _all_ the identical pixels for RLE */ 48 count --; 49 } 50 break; 51 } 52 } 53 54 return count; 55} 56 57int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr , int bpp, int w, 58 int add_rep, int xor_rep, int add_raw, int xor_raw) 59{ 60 int count, x; 61 uint8_t *out = outbuf; 62 63 for(x = 0; x < w; x += count) { 64 /* see if we can encode the next set of pixels with RLE */ 65 if((count = count_pixels(ptr, w-x, bpp, 1)) > 1) { 66 if(out + bpp + 1 > outbuf + out_size) return -1; 67 *out++ = (count ^ xor_rep) + add_rep; 68 memcpy(out, ptr, bpp); 69 out += bpp; 70 } else { 71 /* fall back on uncompressed */ 72 count = count_pixels(ptr, w-x, bpp, 0); 73 if(out + bpp*count >= outbuf + out_size) return -1; 74 *out++ = (count ^ xor_raw) + add_raw; 75 76 memcpy(out, ptr, bpp * count); 77 out += bpp * count; 78 } 79 80 ptr += count * bpp; 81 } 82 83 return out - outbuf; 84} 85