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 "bytestream.h" 23#include "png.h" 24 25const uint8_t ff_pngsig[8] = {137, 80, 78, 71, 13, 10, 26, 10}; 26const uint8_t ff_mngsig[8] = {138, 77, 78, 71, 13, 10, 26, 10}; 27 28/* Mask to determine which y pixels are valid in a pass */ 29const uint8_t ff_png_pass_ymask[NB_PASSES] = { 30 0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 31}; 32 33/* minimum x value */ 34const uint8_t ff_png_pass_xmin[NB_PASSES] = { 35 0, 4, 0, 2, 0, 1, 0 36}; 37 38/* x shift to get row width */ 39const uint8_t ff_png_pass_xshift[NB_PASSES] = { 40 3, 3, 2, 2, 1, 1, 0 41}; 42 43/* Mask to determine which pixels are valid in a pass */ 44const uint8_t ff_png_pass_mask[NB_PASSES] = { 45 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff 46}; 47 48void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size) 49{ 50 if(items >= UINT_MAX / size) 51 return NULL; 52 return av_malloc(items * size); 53} 54 55void ff_png_zfree(void *opaque, void *ptr) 56{ 57 av_free(ptr); 58} 59 60int ff_png_get_nb_channels(int color_type) 61{ 62 int channels; 63 channels = 1; 64 if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) == 65 PNG_COLOR_MASK_COLOR) 66 channels = 3; 67 if (color_type & PNG_COLOR_MASK_ALPHA) 68 channels++; 69 return channels; 70} 71 72/* compute the row size of an interleaved pass */ 73int ff_png_pass_row_size(int pass, int bits_per_pixel, int width) 74{ 75 int shift, xmin, pass_width; 76 77 xmin = ff_png_pass_xmin[pass]; 78 if (width <= xmin) 79 return 0; 80 shift = ff_png_pass_xshift[pass]; 81 pass_width = (width - xmin + (1 << shift) - 1) >> shift; 82 return (pass_width * bits_per_pixel + 7) >> 3; 83} 84