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/*
* RLE encoder
* Copyright (c) 2007 Bobby Bingham
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <string.h>
#include "libavutil/macros.h"
#include "rle.h"
int ff_rle_count_pixels(const uint8_t *start, int len, int bpp, int same)
{
const uint8_t *pos;
int count = 1;
for (pos = start + bpp; count < FFMIN(127, len); pos += bpp, count++) {
if (same != !memcmp(pos - bpp, pos, bpp)) {
if (!same) {
/* if bpp == 1, then 0 1 1 0 is more efficiently encoded as a
* single raw block of pixels. For larger bpp, RLE is as good
* or better */
if (bpp == 1 && count + 1 < FFMIN(127, len) && *pos != *(pos + 1))
continue;
/* if RLE can encode the next block better than as a raw block,
* back up and leave _all_ the identical pixels for RLE */
count--;
}
break;
}
}
return count;
}
int 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)
{
int count, x;
uint8_t *out = outbuf;
for (x = 0; x < w; x += count) {
/* see if we can encode the next set of pixels with RLE */
if ((count = ff_rle_count_pixels(ptr, w - x, bpp, 1)) > 1) {
if (out + bpp + 1 > outbuf + out_size)
return -1;
*out++ = (count ^ xor_rep) + add_rep;
memcpy(out, ptr, bpp);
out += bpp;
} else {
/* fall back on uncompressed */
count = ff_rle_count_pixels(ptr, w - x, bpp, 0);
if (out + bpp * count >= outbuf + out_size)
return -1;
*out++ = (count ^ xor_raw) + add_raw;
memcpy(out, ptr, bpp * count);
out += bpp * count;
}
ptr += count * bpp;
}
return out - outbuf;
}
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