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ffmpeg / libavcodec / png.c @ b958a7f1

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/*
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 * PNG image format
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 * Copyright (c) 2003 Fabrice Bellard.
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#include "avcodec.h"
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#include "bytestream.h"
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#include "png.h"
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const uint8_t ff_pngsig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
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/* Mask to determine which y pixels are valid in a pass */
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const uint8_t ff_png_pass_ymask[NB_PASSES] = {
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    0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55,
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};
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/* minimum x value */
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const uint8_t ff_png_pass_xmin[NB_PASSES] = {
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    0, 4, 0, 2, 0, 1, 0
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};
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/* x shift to get row width */
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const uint8_t ff_png_pass_xshift[NB_PASSES] = {
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    3, 3, 2, 2, 1, 1, 0
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};
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/* Mask to determine which pixels are valid in a pass */
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const uint8_t ff_png_pass_mask[NB_PASSES] = {
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    0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff
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};
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void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size)
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{
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    if(items >= UINT_MAX / size)
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        return NULL;
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    return av_malloc(items * size);
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}
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void ff_png_zfree(void *opaque, void *ptr)
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{
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    av_free(ptr);
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}
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int ff_png_get_nb_channels(int color_type)
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{
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    int channels;
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    channels = 1;
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    if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) ==
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        PNG_COLOR_MASK_COLOR)
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        channels = 3;
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    if (color_type & PNG_COLOR_MASK_ALPHA)
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        channels++;
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    return channels;
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}
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/* compute the row size of an interleaved pass */
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int ff_png_pass_row_size(int pass, int bits_per_pixel, int width)
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{
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    int shift, xmin, pass_width;
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    xmin = ff_png_pass_xmin[pass];
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    if (width <= xmin)
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        return 0;
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    shift = ff_png_pass_xshift[pass];
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    pass_width = (width - xmin + (1 << shift) - 1) >> shift;
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    return (pass_width * bits_per_pixel + 7) >> 3;
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}
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int ff_png_common_init(AVCodecContext *avctx){
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    PNGContext *s = avctx->priv_data;
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    avcodec_get_frame_defaults((AVFrame*)&s->picture);
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    avctx->coded_frame= (AVFrame*)&s->picture;
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//    s->avctx= avctx;
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    return 0;
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}