yading@10: /*
yading@10:  * PNG image format
yading@10:  * Copyright (c) 2003 Fabrice Bellard
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 "png.h"
yading@10: 
yading@10: /* Mask to determine which y pixels are valid in a pass */
yading@10: const uint8_t ff_png_pass_ymask[NB_PASSES] = {
yading@10:     0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55,
yading@10: };
yading@10: 
yading@10: /* minimum x value */
yading@10: static const uint8_t ff_png_pass_xmin[NB_PASSES] = {
yading@10:     0, 4, 0, 2, 0, 1, 0
yading@10: };
yading@10: 
yading@10: /* x shift to get row width */
yading@10: static const uint8_t ff_png_pass_xshift[NB_PASSES] = {
yading@10:     3, 3, 2, 2, 1, 1, 0
yading@10: };
yading@10: 
yading@10: void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size)
yading@10: {
yading@10:     return av_mallocz_array(items, size);
yading@10: }
yading@10: 
yading@10: void ff_png_zfree(void *opaque, void *ptr)
yading@10: {
yading@10:     av_free(ptr);
yading@10: }
yading@10: 
yading@10: int ff_png_get_nb_channels(int color_type)
yading@10: {
yading@10:     int channels;
yading@10:     channels = 1;
yading@10:     if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) ==
yading@10:         PNG_COLOR_MASK_COLOR)
yading@10:         channels = 3;
yading@10:     if (color_type & PNG_COLOR_MASK_ALPHA)
yading@10:         channels++;
yading@10:     return channels;
yading@10: }
yading@10: 
yading@10: /* compute the row size of an interleaved pass */
yading@10: int ff_png_pass_row_size(int pass, int bits_per_pixel, int width)
yading@10: {
yading@10:     int shift, xmin, pass_width;
yading@10: 
yading@10:     xmin = ff_png_pass_xmin[pass];
yading@10:     if (width <= xmin)
yading@10:         return 0;
yading@10:     shift = ff_png_pass_xshift[pass];
yading@10:     pass_width = (width - xmin + (1 << shift) - 1) >> shift;
yading@10:     return (pass_width * bits_per_pixel + 7) >> 3;
yading@10: }