Libav
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00001 /* 00002 * PNG image format 00003 * Copyright (c) 2003 Fabrice Bellard 00004 * 00005 * This file is part of FFmpeg. 00006 * 00007 * FFmpeg is free software; you can redistribute it and/or 00008 * modify it under the terms of the GNU Lesser General Public 00009 * License as published by the Free Software Foundation; either 00010 * version 2.1 of the License, or (at your option) any later version. 00011 * 00012 * FFmpeg is distributed in the hope that it will be useful, 00013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00015 * Lesser General Public License for more details. 00016 * 00017 * You should have received a copy of the GNU Lesser General Public 00018 * License along with FFmpeg; if not, write to the Free Software 00019 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00020 */ 00021 #include "avcodec.h" 00022 #include "bytestream.h" 00023 #include "png.h" 00024 00025 const uint8_t ff_pngsig[8] = {137, 80, 78, 71, 13, 10, 26, 10}; 00026 const uint8_t ff_mngsig[8] = {138, 77, 78, 71, 13, 10, 26, 10}; 00027 00028 /* Mask to determine which y pixels are valid in a pass */ 00029 const uint8_t ff_png_pass_ymask[NB_PASSES] = { 00030 0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 00031 }; 00032 00033 /* minimum x value */ 00034 const uint8_t ff_png_pass_xmin[NB_PASSES] = { 00035 0, 4, 0, 2, 0, 1, 0 00036 }; 00037 00038 /* x shift to get row width */ 00039 const uint8_t ff_png_pass_xshift[NB_PASSES] = { 00040 3, 3, 2, 2, 1, 1, 0 00041 }; 00042 00043 /* Mask to determine which pixels are valid in a pass */ 00044 const uint8_t ff_png_pass_mask[NB_PASSES] = { 00045 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff 00046 }; 00047 00048 void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size) 00049 { 00050 if(items >= UINT_MAX / size) 00051 return NULL; 00052 return av_malloc(items * size); 00053 } 00054 00055 void ff_png_zfree(void *opaque, void *ptr) 00056 { 00057 av_free(ptr); 00058 } 00059 00060 int ff_png_get_nb_channels(int color_type) 00061 { 00062 int channels; 00063 channels = 1; 00064 if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) == 00065 PNG_COLOR_MASK_COLOR) 00066 channels = 3; 00067 if (color_type & PNG_COLOR_MASK_ALPHA) 00068 channels++; 00069 return channels; 00070 } 00071 00072 /* compute the row size of an interleaved pass */ 00073 int ff_png_pass_row_size(int pass, int bits_per_pixel, int width) 00074 { 00075 int shift, xmin, pass_width; 00076 00077 xmin = ff_png_pass_xmin[pass]; 00078 if (width <= xmin) 00079 return 0; 00080 shift = ff_png_pass_xshift[pass]; 00081 pass_width = (width - xmin + (1 << shift) - 1) >> shift; 00082 return (pass_width * bits_per_pixel + 7) >> 3; 00083 }