/*

 * PNG image format

 * Copyright (c) 2003 Fabrice Bellard

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include <stdint.h>

#include "libavutil/mem.h"

#include "png.h"

/* Mask to determine which y pixels are valid in a pass */

const uint8_t ff_png_pass_ymask[NB_PASSES] = {

    0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55,

};

/* minimum x value */

static const uint8_t ff_png_pass_xmin[NB_PASSES] = {

    0, 4, 0, 2, 0, 1, 0

};

/* x shift to get row width */

static const uint8_t ff_png_pass_xshift[NB_PASSES] = {

    3, 3, 2, 2, 1, 1, 0

};

int ff_png_get_nb_channels(int color_type)

{

    int channels;

    channels = 1;

    if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) ==

        PNG_COLOR_MASK_COLOR)

        channels = 3;

    if (color_type & PNG_COLOR_MASK_ALPHA)

        channels++;

    return channels;

}

/* compute the row size of an interleaved pass */

int ff_png_pass_row_size(int pass, int bits_per_pixel, int width)

{

    int shift, xmin, pass_width;

    xmin = ff_png_pass_xmin[pass];

    if (width <= xmin)

        return 0;

    shift      = ff_png_pass_xshift[pass];

    pass_width = (width - xmin + (1 << shift) - 1) >> shift;

    return (pass_width * bits_per_pixel + 7) >> 3;

}