Subversion Repositories Kolibri OS

Rev

Go to most recent revision | Blame | Last modification | View Log | RSS feed

  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. #include "libavutil/common.h"
  24.  
  25. /**
  26.  * Count up to 127 consecutive pixels which are either all the same or
  27.  * all differ from the previous and next pixels.
  28.  * @param start Pointer to the first pixel
  29.  * @param len Maximum number of pixels
  30.  * @param bpp Bytes per pixel
  31.  * @param same 1 if searching for identical pixel values.  0 for differing
  32.  * @return Number of matching consecutive pixels found
  33.  */
  34. static int count_pixels(const uint8_t *start, int len, int bpp, int same)
  35. {
  36.     const uint8_t *pos;
  37.     int count = 1;
  38.  
  39.     for(pos = start + bpp; count < FFMIN(127, len); pos += bpp, count ++) {
  40.         if(same != !memcmp(pos-bpp, pos, bpp)) {
  41.             if(!same) {
  42.                 /* if bpp == 1, then 0 1 1 0 is more efficiently encoded as a single
  43.                  * raw block of pixels.  for larger bpp, RLE is as good or better */
  44.                 if(bpp == 1 && count + 1 < FFMIN(127, len) && *pos != *(pos+1))
  45.                     continue;
  46.  
  47.                 /* if RLE can encode the next block better than as a raw block,
  48.                  * back up and leave _all_ the identical pixels for RLE */
  49.                 count --;
  50.             }
  51.             break;
  52.         }
  53.     }
  54.  
  55.     return count;
  56. }
  57.  
  58. int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr , int bpp, int w,
  59.                   int add_rep, int xor_rep, int add_raw, int xor_raw)
  60. {
  61.     int count, x;
  62.     uint8_t *out = outbuf;
  63.  
  64.     for(x = 0; x < w; x += count) {
  65.         /* see if we can encode the next set of pixels with RLE */
  66.         if((count = count_pixels(ptr, w-x, bpp, 1)) > 1) {
  67.             if(out + bpp + 1 > outbuf + out_size) return -1;
  68.             *out++ = (count ^ xor_rep) + add_rep;
  69.             memcpy(out, ptr, bpp);
  70.             out += bpp;
  71.         } else {
  72.             /* fall back on uncompressed */
  73.             count = count_pixels(ptr, w-x, bpp, 0);
  74.             if(out + bpp*count >= outbuf + out_size) return -1;
  75.             *out++ = (count ^ xor_raw) + add_raw;
  76.  
  77.             memcpy(out, ptr, bpp * count);
  78.             out += bpp * count;
  79.         }
  80.  
  81.         ptr += count * bpp;
  82.     }
  83.  
  84.     return out - outbuf;
  85. }
  86.