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
23 #include "libavutil/common.h"
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(127, 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(127, 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 */
58 int 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
)
62 uint8_t *out
= outbuf
;
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
);
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
;
77 memcpy(out
, ptr
, bpp
* count
);