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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 "avcodec.h"
#include "rle.h"
/**
* Count up to 127 consecutive pixels which are either all the same or
* all differ from the previous and next pixels.
* @param start Pointer to the first pixel
* @param len Maximum number of pixels
* @param bpp Bytes per pixel
* @param same 1 if searching for identical pixel values. 0 for differing
* @return Number of matching consecutive pixels found
*/
static int 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(128, 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(128, 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;
}
/**
* RLE compress the row, with maximum size of out_size. Value before repeated bytes is (count ^ xor) + add.
* @param outbuf Output buffer
* @param out_size Maximum output size
* @param ptr Input buffer
* @param bpp Bytes per pixel
* @param w Image width
* @return Size of output in bytes, or -1 if larger than out_size
*/
int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr , int bpp, int w, int8_t add, uint8_t xor)
{
int count, x;
uint8_t *out;
out = outbuf;
for(x = 0; x < w; x += count) {
/* see if we can encode the next set of pixels with RLE */
if((count = count_pixels(ptr, w-x, bpp, 1)) > 1) {
if(out + bpp + 1 > outbuf + out_size) return -1;
*out++ = (count ^ xor) + add;
memcpy(out, ptr, bpp);
out += bpp;
} else {
/* fall back on uncompressed */
count = count_pixels(ptr, w-x, bpp, 0);
*out++ = count - 1;
if(out + bpp*count > outbuf + out_size) return -1;
memcpy(out, ptr, bpp * count);
out += bpp * count;
}
ptr += count * bpp;
}
return out - outbuf;
}
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