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