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