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/libavcodec/rle.c

http://github.com/FFmpeg/FFmpeg
C | 82 lines | 43 code | 12 blank | 27 comment | 14 complexity | 069f03844003044d6b8511b769d672f6 MD5 | raw file
 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 "libavutil/common.h"
23
24#include "avcodec.h"
25#include "rle.h"
26
27int ff_rle_count_pixels(const uint8_t *start, int len, int bpp, int same)
28{
29    const uint8_t *pos;
30    int count = 1;
31
32    for (pos = start + bpp; count < FFMIN(127, len); pos += bpp, count++) {
33        if (same != !memcmp(pos - bpp, pos, bpp)) {
34            if (!same) {
35                /* if bpp == 1, then 0 1 1 0 is more efficiently encoded as a
36                 * single raw block of pixels. For larger bpp, RLE is as good
37                 * or better */
38                if (bpp == 1 && count + 1 < FFMIN(127, len) && *pos != *(pos + 1))
39                    continue;
40
41                /* if RLE can encode the next block better than as a raw block,
42                 * back up and leave _all_ the identical pixels for RLE */
43                count--;
44            }
45            break;
46        }
47    }
48
49    return count;
50}
51
52int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr, int bpp,
53                  int w, int add_rep, int xor_rep, int add_raw, int xor_raw)
54{
55    int count, x;
56    uint8_t *out = outbuf;
57
58    for (x = 0; x < w; x += count) {
59        /* see if we can encode the next set of pixels with RLE */
60        if ((count = ff_rle_count_pixels(ptr, w - x, bpp, 1)) > 1) {
61            if (out + bpp + 1 > outbuf + out_size)
62                return -1;
63
64            *out++ = (count ^ xor_rep) + add_rep;
65            memcpy(out, ptr, bpp);
66            out += bpp;
67        } else {
68            /* fall back on uncompressed */
69            count = ff_rle_count_pixels(ptr, w - x, bpp, 0);
70            if (out + bpp * count >= outbuf + out_size)
71                return -1;
72
73            *out++ = (count ^ xor_raw) + add_raw;
74            memcpy(out, ptr, bpp * count);
75            out += bpp * count;
76        }
77
78        ptr += count * bpp;
79    }
80
81    return out - outbuf;
82}