From 1ca286e194226a05cc3d4aed50ee780e7f078721 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Tue, 3 Apr 2007 01:01:46 +0000 Subject: generic rle encoder by Bartlomiej Wolowiec b.wolowiec students mimuw edu pl Originally committed as revision 8598 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/rle.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 96 insertions(+) create mode 100644 libavcodec/rle.c (limited to 'libavcodec/rle.c') diff --git a/libavcodec/rle.c b/libavcodec/rle.c new file mode 100644 index 0000000000..aa05f6d513 --- /dev/null +++ b/libavcodec/rle.c @@ -0,0 +1,96 @@ +/* + * 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; +} -- cgit v1.2.3