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 */
34static 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
58int 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