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
22 #include <string.h>
23
24 #include "libavutil/macros.h"
25
26 #include "rle.h"
27
ff_rle_count_pixels(const uint8_t *start, int len, int bpp, int same)28 int ff_rle_count_pixels(const uint8_t *start, int len, int bpp, int same)
29 {
30 const uint8_t *pos;
31 int count = 1;
32
33 for (pos = start + bpp; count < FFMIN(127, len); pos += bpp, count++) {
34 if (same != !memcmp(pos - bpp, pos, bpp)) {
35 if (!same) {
36 /* if bpp == 1, then 0 1 1 0 is more efficiently encoded as a
37 * single raw block of pixels. For larger bpp, RLE is as good
38 * or better */
39 if (bpp == 1 && count + 1 < FFMIN(127, len) && *pos != *(pos + 1))
40 continue;
41
42 /* if RLE can encode the next block better than as a raw block,
43 * back up and leave _all_ the identical pixels for RLE */
44 count--;
45 }
46 break;
47 }
48 }
49
50 return count;
51 }
52
ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr, int bpp, int w, int add_rep, int xor_rep, int add_raw, int xor_raw)53 int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr, int bpp,
54 int w, int add_rep, int xor_rep, int add_raw, int xor_raw)
55 {
56 int count, x;
57 uint8_t *out = outbuf;
58
59 for (x = 0; x < w; x += count) {
60 /* see if we can encode the next set of pixels with RLE */
61 if ((count = ff_rle_count_pixels(ptr, w - x, bpp, 1)) > 1) {
62 if (out + bpp + 1 > outbuf + out_size)
63 return -1;
64
65 *out++ = (count ^ xor_rep) + add_rep;
66 memcpy(out, ptr, bpp);
67 out += bpp;
68 } else {
69 /* fall back on uncompressed */
70 count = ff_rle_count_pixels(ptr, w - x, bpp, 0);
71 if (out + bpp * count >= outbuf + out_size)
72 return -1;
73
74 *out++ = (count ^ xor_raw) + add_raw;
75 memcpy(out, ptr, bpp * count);
76 out += bpp * count;
77 }
78
79 ptr += count * bpp;
80 }
81
82 return out - outbuf;
83 }
84