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 22#include <stdint.h> 23#include "libavutil/mem.h" 24#include "png.h" 25 26/* Mask to determine which y pixels are valid in a pass */ 27const uint8_t ff_png_pass_ymask[NB_PASSES] = { 28 0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 29}; 30 31/* minimum x value */ 32static const uint8_t ff_png_pass_xmin[NB_PASSES] = { 33 0, 4, 0, 2, 0, 1, 0 34}; 35 36/* x shift to get row width */ 37static const uint8_t ff_png_pass_xshift[NB_PASSES] = { 38 3, 3, 2, 2, 1, 1, 0 39}; 40 41int ff_png_get_nb_channels(int color_type) 42{ 43 int channels; 44 channels = 1; 45 if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) == 46 PNG_COLOR_MASK_COLOR) 47 channels = 3; 48 if (color_type & PNG_COLOR_MASK_ALPHA) 49 channels++; 50 return channels; 51} 52 53/* compute the row size of an interleaved pass */ 54int ff_png_pass_row_size(int pass, int bits_per_pixel, int width) 55{ 56 int shift, xmin, pass_width; 57 58 xmin = ff_png_pass_xmin[pass]; 59 if (width <= xmin) 60 return 0; 61 shift = ff_png_pass_xshift[pass]; 62 pass_width = (width - xmin + (1 << shift) - 1) >> shift; 63 return (pass_width * bits_per_pixel + 7) >> 3; 64} 65