3 * Copyright (c) 2007 Bobby Bingham
5 * This file is part of FFmpeg.
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.
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.
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
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
34 static int count_pixels(const uint8_t *start, int len, int bpp, int same)
39 for(pos = start + bpp; count < FFMIN(128, len); pos += bpp, count ++) {
40 if(same != !memcmp(pos-bpp, pos, bpp)) {
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(128, len) && *pos != *(pos+1))
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 */
59 * RLE compress the row, with maximum size of out_size. Value before repeated bytes is (count ^ xor) + add.
60 * @param outbuf Output buffer
61 * @param out_size Maximum output size
62 * @param ptr Input buffer
63 * @param bpp Bytes per pixel
64 * @param w Image width
65 * @return Size of output in bytes, or -1 if larger than out_size
67 int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr , int bpp, int w, int8_t add, uint8_t xor)
75 for(x = 0; x < w; x += count) {
76 /* see if we can encode the next set of pixels with RLE */
77 if((count = count_pixels(ptr, w-x, bpp, 1)) > 1) {
78 if(out + bpp + 1 > outbuf + out_size) return -1;
79 *out++ = (count ^ xor) + add;
80 memcpy(out, ptr, bpp);
83 /* fall back on uncompressed */
84 count = count_pixels(ptr, w-x, bpp, 0);
87 if(out + bpp*count > outbuf + out_size) return -1;
88 memcpy(out, ptr, bpp * count);