yading@10: /*
yading@10:  * RLE encoder
yading@10:  * Copyright (c) 2007 Bobby Bingham
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: #include "avcodec.h"
yading@10: #include "rle.h"
yading@10: #include "libavutil/common.h"
yading@10: 
yading@10: /**
yading@10:  * Count up to 127 consecutive pixels which are either all the same or
yading@10:  * all differ from the previous and next pixels.
yading@10:  * @param start Pointer to the first pixel
yading@10:  * @param len Maximum number of pixels
yading@10:  * @param bpp Bytes per pixel
yading@10:  * @param same 1 if searching for identical pixel values.  0 for differing
yading@10:  * @return Number of matching consecutive pixels found
yading@10:  */
yading@10: static int count_pixels(const uint8_t *start, int len, int bpp, int same)
yading@10: {
yading@10:     const uint8_t *pos;
yading@10:     int count = 1;
yading@10: 
yading@10:     for(pos = start + bpp; count < FFMIN(127, len); pos += bpp, count ++) {
yading@10:         if(same != !memcmp(pos-bpp, pos, bpp)) {
yading@10:             if(!same) {
yading@10:                 /* if bpp == 1, then 0 1 1 0 is more efficiently encoded as a single
yading@10:                  * raw block of pixels.  for larger bpp, RLE is as good or better */
yading@10:                 if(bpp == 1 && count + 1 < FFMIN(127, len) && *pos != *(pos+1))
yading@10:                     continue;
yading@10: 
yading@10:                 /* if RLE can encode the next block better than as a raw block,
yading@10:                  * back up and leave _all_ the identical pixels for RLE */
yading@10:                 count --;
yading@10:             }
yading@10:             break;
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     return count;
yading@10: }
yading@10: 
yading@10: int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr , int bpp, int w,
yading@10:                   int add_rep, int xor_rep, int add_raw, int xor_raw)
yading@10: {
yading@10:     int count, x;
yading@10:     uint8_t *out = outbuf;
yading@10: 
yading@10:     for(x = 0; x < w; x += count) {
yading@10:         /* see if we can encode the next set of pixels with RLE */
yading@10:         if((count = count_pixels(ptr, w-x, bpp, 1)) > 1) {
yading@10:             if(out + bpp + 1 > outbuf + out_size) return -1;
yading@10:             *out++ = (count ^ xor_rep) + add_rep;
yading@10:             memcpy(out, ptr, bpp);
yading@10:             out += bpp;
yading@10:         } else {
yading@10:             /* fall back on uncompressed */
yading@10:             count = count_pixels(ptr, w-x, bpp, 0);
yading@10:             if(out + bpp*count >= outbuf + out_size) return -1;
yading@10:             *out++ = (count ^ xor_raw) + add_raw;
yading@10: 
yading@10:             memcpy(out, ptr, bpp * count);
yading@10:             out += bpp * count;
yading@10:         }
yading@10: 
yading@10:         ptr += count * bpp;
yading@10:     }
yading@10: 
yading@10:     return out - outbuf;
yading@10: }