1/* 2 * PNG image format 3 * Copyright (c) 2003 Fabrice Bellard 4 * 5 * This file is part of FFmpeg. 6 * 7 * FFmpeg is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * FFmpeg is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with FFmpeg; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21#include "avcodec.h" 22#include "png.h" 23 24/* Mask to determine which y pixels are valid in a pass */ 25const uint8_t ff_png_pass_ymask[NB_PASSES] = { 26 0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 27}; 28 29/* minimum x value */ 30static const uint8_t ff_png_pass_xmin[NB_PASSES] = { 31 0, 4, 0, 2, 0, 1, 0 32}; 33 34/* x shift to get row width */ 35static const uint8_t ff_png_pass_xshift[NB_PASSES] = { 36 3, 3, 2, 2, 1, 1, 0 37}; 38 39void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size) 40{ 41 return av_mallocz_array(items, size); 42} 43 44void ff_png_zfree(void *opaque, void *ptr) 45{ 46 av_free(ptr); 47} 48 49int ff_png_get_nb_channels(int color_type) 50{ 51 int channels; 52 channels = 1; 53 if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) == 54 PNG_COLOR_MASK_COLOR) 55 channels = 3; 56 if (color_type & PNG_COLOR_MASK_ALPHA) 57 channels++; 58 return channels; 59} 60 61/* compute the row size of an interleaved pass */ 62int ff_png_pass_row_size(int pass, int bits_per_pixel, int width) 63{ 64 int shift, xmin, pass_width; 65 66 xmin = ff_png_pass_xmin[pass]; 67 if (width <= xmin) 68 return 0; 69 shift = ff_png_pass_xshift[pass]; 70 pass_width = (width - xmin + (1 << shift) - 1) >> shift; 71 return (pass_width * bits_per_pixel + 7) >> 3; 72} 73