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libavcodec
png.c
Go to the documentation of this file.
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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 Libav.
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*
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* Libav 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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* Libav 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 Libav; 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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const
uint8_t
ff_mngsig
[8] = {138, 77, 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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static
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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static
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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return
av_mallocz_array
(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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}