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ffmpeg/libavcodec/pngdec.c

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/*
* 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
*/
//#define DEBUG
#include "libavutil/imgutils.h"
#include "avcodec.h"
#include "bytestream.h"
#include "png.h"
#include "pngdsp.h"
/* TODO:
* - add 16 bit depth support
*/
#include <zlib.h>
//#define DEBUG
typedef struct PNGDecContext {
PNGDSPContext dsp;
GetByteContext gb;
AVFrame picture1, picture2;
AVFrame *current_picture, *last_picture;
int state;
int width, height;
int bit_depth;
int color_type;
int compression_type;
int interlace_type;
int filter_type;
int channels;
int bits_per_pixel;
int bpp;
uint8_t *image_buf;
int image_linesize;
uint32_t palette[256];
uint8_t *crow_buf;
uint8_t *last_row;
uint8_t *tmp_row;
int pass;
int crow_size; /* compressed row size (include filter type) */
int row_size; /* decompressed row size */
int pass_row_size; /* decompress row size of the current pass */
int y;
z_stream zstream;
} PNGDecContext;
/* Mask to determine which pixels are valid in a pass */
static const uint8_t png_pass_mask[NB_PASSES] = {
0x01, 0x01, 0x11, 0x11, 0x55, 0x55, 0xff,
};
/* Mask to determine which y pixels can be written in a pass */
static const uint8_t png_pass_dsp_ymask[NB_PASSES] = {
0xff, 0xff, 0x0f, 0xff, 0x33, 0xff, 0x55,
};
/* Mask to determine which pixels to overwrite while displaying */
static const uint8_t png_pass_dsp_mask[NB_PASSES] = {
0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff
};
/* NOTE: we try to construct a good looking image at each pass. width
is the original image width. We also do pixel format conversion at
this stage */
static void png_put_interlaced_row(uint8_t *dst, int width,
int bits_per_pixel, int pass,
int color_type, const uint8_t *src)
{
int x, mask, dsp_mask, j, src_x, b, bpp;
uint8_t *d;
const uint8_t *s;
mask = png_pass_mask[pass];
dsp_mask = png_pass_dsp_mask[pass];
switch(bits_per_pixel) {
case 1:
src_x = 0;
for(x = 0; x < width; x++) {
j = (x & 7);
if ((dsp_mask << j) & 0x80) {
b = (src[src_x >> 3] >> (7 - (src_x & 7))) & 1;
dst[x >> 3] &= 0xFF7F>>j;
dst[x >> 3] |= b << (7 - j);
}
if ((mask << j) & 0x80)
src_x++;
}
break;
case 2:
src_x = 0;
for(x = 0; x < width; x++) {
int j2 = 2*(x&3);
j = (x & 7);
if ((dsp_mask << j) & 0x80) {
b = (src[src_x >> 2] >> (6 - 2*(src_x & 3))) & 3;
dst[x >> 2] &= 0xFF3F>>j2;
dst[x >> 2] |= b << (6 - j2);
}
if ((mask << j) & 0x80)
src_x++;
}
break;
case 4:
src_x = 0;
for(x = 0; x < width; x++) {
int j2 = 4*(x&1);
j = (x & 7);
if ((dsp_mask << j) & 0x80) {
b = (src[src_x >> 1] >> (4 - 4*(src_x & 1))) & 15;
dst[x >> 1] &= 0xFF0F>>j2;
dst[x >> 1] |= b << (4 - j2);
}
if ((mask << j) & 0x80)
src_x++;
}
break;
default:
bpp = bits_per_pixel >> 3;
d = dst;
s = src;
for(x = 0; x < width; x++) {
j = x & 7;
if ((dsp_mask << j) & 0x80) {
memcpy(d, s, bpp);
}
d += bpp;
if ((mask << j) & 0x80)
s += bpp;
}
break;
}
}
void ff_add_png_paeth_prediction(uint8_t *dst, uint8_t *src, uint8_t *top, int w, int bpp)
{
int i;
for(i = 0; i < w; i++) {
int a, b, c, p, pa, pb, pc;
a = dst[i - bpp];
b = top[i];
c = top[i - bpp];
p = b - c;
pc = a - c;
pa = abs(p);
pb = abs(pc);
pc = abs(p + pc);
if (pa <= pb && pa <= pc)
p = a;
else if (pb <= pc)
p = b;
else
p = c;
dst[i] = p + src[i];
}
}
#define UNROLL1(bpp, op) {\
r = dst[0];\
if(bpp >= 2) g = dst[1];\
if(bpp >= 3) b = dst[2];\
if(bpp >= 4) a = dst[3];\
for(; i < size; i+=bpp) {\
dst[i+0] = r = op(r, src[i+0], last[i+0]);\
if(bpp == 1) continue;\
dst[i+1] = g = op(g, src[i+1], last[i+1]);\
if(bpp == 2) continue;\
dst[i+2] = b = op(b, src[i+2], last[i+2]);\
if(bpp == 3) continue;\
dst[i+3] = a = op(a, src[i+3], last[i+3]);\
}\
}
#define UNROLL_FILTER(op)\
if(bpp == 1) UNROLL1(1, op)\
else if(bpp == 2) UNROLL1(2, op)\
else if(bpp == 3) UNROLL1(3, op)\
else if(bpp == 4) UNROLL1(4, op)\
else {\
for (; i < size; i += bpp) {\
int j;\
for (j = 0; j < bpp; j++)\
dst[i+j] = op(dst[i+j-bpp], src[i+j], last[i+j]);\
}\
}
/* NOTE: 'dst' can be equal to 'last' */
static void png_filter_row(PNGDSPContext *dsp, uint8_t *dst, int filter_type,
uint8_t *src, uint8_t *last, int size, int bpp)
{
int i, p, r, g, b, a;
switch(filter_type) {
case PNG_FILTER_VALUE_NONE:
memcpy(dst, src, size);
break;
case PNG_FILTER_VALUE_SUB:
for(i = 0; i < bpp; i++) {
dst[i] = src[i];
}
if(bpp == 4) {
p = *(int*)dst;
for(; i < size; i+=bpp) {
int s = *(int*)(src+i);
p = ((s&0x7f7f7f7f) + (p&0x7f7f7f7f)) ^ ((s^p)&0x80808080);
*(int*)(dst+i) = p;
}
} else {
#define OP_SUB(x,s,l) x+s
UNROLL_FILTER(OP_SUB);
}
break;
case PNG_FILTER_VALUE_UP:
dsp->add_bytes_l2(dst, src, last, size);
break;
case PNG_FILTER_VALUE_AVG:
for(i = 0; i < bpp; i++) {
p = (last[i] >> 1);
dst[i] = p + src[i];
}
#define OP_AVG(x,s,l) (((x + l) >> 1) + s) & 0xff
UNROLL_FILTER(OP_AVG);
break;
case PNG_FILTER_VALUE_PAETH:
for(i = 0; i < bpp; i++) {
p = last[i];
dst[i] = p + src[i];
}
if(bpp > 2 && size > 4) {
// would write off the end of the array if we let it process the last pixel with bpp=3
int w = bpp==4 ? size : size-3;
dsp->add_paeth_prediction(dst+i, src+i, last+i, w-i, bpp);
i = w;
}
ff_add_png_paeth_prediction(dst+i, src+i, last+i, size-i, bpp);
break;
}
}
/* This used to be called "deloco" in FFmpeg
* and is actually an inverse reversible colorspace transformation */
#define YUV2RGB(NAME, TYPE) \
static void deloco_ ## NAME(TYPE *dst, int size, int alpha) \
{ \
int i; \
for (i = 0; i < size; i += 3 + alpha) { \
int g = dst [i+1]; \
dst[i+0] += g; \
dst[i+2] += g; \
} \
}
YUV2RGB(rgb8, uint8_t)
YUV2RGB(rgb16, uint16_t)
/* process exactly one decompressed row */
static void png_handle_row(PNGDecContext *s)
{
uint8_t *ptr, *last_row;
int got_line;
if (!s->interlace_type) {
ptr = s->image_buf + s->image_linesize * s->y;
if (s->y == 0)
last_row = s->last_row;
else
last_row = ptr - s->image_linesize;
png_filter_row(&s->dsp, ptr, s->crow_buf[0], s->crow_buf + 1,
last_row, s->row_size, s->bpp);
/* loco lags by 1 row so that it doesn't interfere with top prediction */
if (s->filter_type == PNG_FILTER_TYPE_LOCO && s->y > 0) {
if (s->bit_depth == 16) {
deloco_rgb16((uint16_t *)(ptr - s->image_linesize), s->row_size / 2,
s->color_type == PNG_COLOR_TYPE_RGB_ALPHA);
} else {
deloco_rgb8(ptr - s->image_linesize, s->row_size,
s->color_type == PNG_COLOR_TYPE_RGB_ALPHA);
}
}
s->y++;
if (s->y == s->height) {
s->state |= PNG_ALLIMAGE;
if (s->filter_type == PNG_FILTER_TYPE_LOCO) {
if (s->bit_depth == 16) {
deloco_rgb16((uint16_t *)ptr, s->row_size / 2,
s->color_type == PNG_COLOR_TYPE_RGB_ALPHA);
} else {
deloco_rgb8(ptr, s->row_size,
s->color_type == PNG_COLOR_TYPE_RGB_ALPHA);
}
}
}
} else {
got_line = 0;
for(;;) {
ptr = s->image_buf + s->image_linesize * s->y;
if ((ff_png_pass_ymask[s->pass] << (s->y & 7)) & 0x80) {
/* if we already read one row, it is time to stop to
wait for the next one */
if (got_line)
break;
png_filter_row(&s->dsp, s->tmp_row, s->crow_buf[0], s->crow_buf + 1,
s->last_row, s->pass_row_size, s->bpp);
FFSWAP(uint8_t*, s->last_row, s->tmp_row);
got_line = 1;
}
if ((png_pass_dsp_ymask[s->pass] << (s->y & 7)) & 0x80) {
png_put_interlaced_row(ptr, s->width, s->bits_per_pixel, s->pass,
s->color_type, s->last_row);
}
s->y++;
if (s->y == s->height) {
memset(s->last_row, 0, s->row_size);
for(;;) {
if (s->pass == NB_PASSES - 1) {
s->state |= PNG_ALLIMAGE;
goto the_end;
} else {
s->pass++;
s->y = 0;
s->pass_row_size = ff_png_pass_row_size(s->pass,
s->bits_per_pixel,
s->width);
s->crow_size = s->pass_row_size + 1;
if (s->pass_row_size != 0)
break;
/* skip pass if empty row */
}
}
}
}
the_end: ;
}
}
static int png_decode_idat(PNGDecContext *s, int length)
{
int ret;
s->zstream.avail_in = FFMIN(length, bytestream2_get_bytes_left(&s->gb));
s->zstream.next_in = s->gb.buffer;
bytestream2_skip(&s->gb, length);
/* decode one line if possible */
while (s->zstream.avail_in > 0) {
ret = inflate(&s->zstream, Z_PARTIAL_FLUSH);
if (ret != Z_OK && ret != Z_STREAM_END) {
return -1;
}
if (s->zstream.avail_out == 0) {
if (!(s->state & PNG_ALLIMAGE)) {
png_handle_row(s);
}
s->zstream.avail_out = s->crow_size;
s->zstream.next_out = s->crow_buf;
}
}
return 0;
}
static int decode_frame(AVCodecContext *avctx,
void *data, int *data_size,
AVPacket *avpkt)
{
const uint8_t *buf = avpkt->data;
int buf_size = avpkt->size;
PNGDecContext * const s = avctx->priv_data;
AVFrame *picture = data;
AVFrame *p;
uint8_t *crow_buf_base = NULL;
uint32_t tag, length;
int ret;
FFSWAP(AVFrame *, s->current_picture, s->last_picture);
avctx->coded_frame= s->current_picture;
p = s->current_picture;
/* check signature */
if (buf_size < 8 ||
memcmp(buf, ff_pngsig, 8) != 0 &&
memcmp(buf, ff_mngsig, 8) != 0) {
av_log(avctx, AV_LOG_ERROR, "Missing png signature\n");
return -1;
}
bytestream2_init(&s->gb, buf + 8, buf_size - 8);
s->y=
s->state=0;
// memset(s, 0, sizeof(PNGDecContext));
/* init the zlib */
s->zstream.zalloc = ff_png_zalloc;
s->zstream.zfree = ff_png_zfree;
s->zstream.opaque = NULL;
ret = inflateInit(&s->zstream);
if (ret != Z_OK)
return -1;
for(;;) {
if (bytestream2_get_bytes_left(&s->gb) <= 0) {
av_log(avctx, AV_LOG_ERROR, "No bytes left\n");
goto fail;
}
length = bytestream2_get_be32(&s->gb);
if (length > 0x7fffffff || length > bytestream2_get_bytes_left(&s->gb)) {
av_log(avctx, AV_LOG_ERROR, "chunk too big\n");
goto fail;
}
tag = bytestream2_get_le32(&s->gb);
if (avctx->debug & FF_DEBUG_STARTCODE)
av_log(avctx, AV_LOG_DEBUG, "png: tag=%c%c%c%c length=%u\n",
(tag & 0xff),
((tag >> 8) & 0xff),
((tag >> 16) & 0xff),
((tag >> 24) & 0xff), length);
switch(tag) {
case MKTAG('I', 'H', 'D', 'R'):
if (length != 13)
goto fail;
s->width = bytestream2_get_be32(&s->gb);
s->height = bytestream2_get_be32(&s->gb);
if(av_image_check_size(s->width, s->height, 0, avctx)){
s->width= s->height= 0;
av_log(avctx, AV_LOG_ERROR, "Invalid image size\n");
goto fail;
}
s->bit_depth = bytestream2_get_byte(&s->gb);
s->color_type = bytestream2_get_byte(&s->gb);
s->compression_type = bytestream2_get_byte(&s->gb);
s->filter_type = bytestream2_get_byte(&s->gb);
s->interlace_type = bytestream2_get_byte(&s->gb);
bytestream2_skip(&s->gb, 4); /* crc */
s->state |= PNG_IHDR;
if (avctx->debug & FF_DEBUG_PICT_INFO)
av_log(avctx, AV_LOG_DEBUG, "width=%d height=%d depth=%d color_type=%d compression_type=%d filter_type=%d interlace_type=%d\n",
s->width, s->height, s->bit_depth, s->color_type,
s->compression_type, s->filter_type, s->interlace_type);
break;
case MKTAG('I', 'D', 'A', 'T'):
if (!(s->state & PNG_IHDR)) {
av_log(avctx, AV_LOG_ERROR, "IDAT without IHDR\n");
goto fail;
}
if (!(s->state & PNG_IDAT)) {
/* init image info */
avctx->width = s->width;
avctx->height = s->height;
s->channels = ff_png_get_nb_channels(s->color_type);
s->bits_per_pixel = s->bit_depth * s->channels;
s->bpp = (s->bits_per_pixel + 7) >> 3;
s->row_size = (avctx->width * s->bits_per_pixel + 7) >> 3;
if ((s->bit_depth == 2 || s->bit_depth == 4 || s->bit_depth == 8) &&
s->color_type == PNG_COLOR_TYPE_RGB) {
avctx->pix_fmt = PIX_FMT_RGB24;
} else if ((s->bit_depth == 2 || s->bit_depth == 4 || s->bit_depth == 8) &&
s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
avctx->pix_fmt = PIX_FMT_RGBA;
} else if ((s->bit_depth == 2 || s->bit_depth == 4 || s->bit_depth == 8) &&
s->color_type == PNG_COLOR_TYPE_GRAY) {
avctx->pix_fmt = PIX_FMT_GRAY8;
} else if (s->bit_depth == 16 &&
s->color_type == PNG_COLOR_TYPE_GRAY) {
avctx->pix_fmt = PIX_FMT_GRAY16BE;
} else if (s->bit_depth == 16 &&
s->color_type == PNG_COLOR_TYPE_RGB) {
avctx->pix_fmt = PIX_FMT_RGB48BE;
} else if (s->bit_depth == 16 &&
s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
avctx->pix_fmt = PIX_FMT_RGBA64BE;
} else if (s->color_type == PNG_COLOR_TYPE_PALETTE) {
avctx->pix_fmt = PIX_FMT_PAL8;
} else if (s->bit_depth == 1) {
avctx->pix_fmt = PIX_FMT_MONOBLACK;
} else if (s->bit_depth == 8 &&
s->color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
avctx->pix_fmt = PIX_FMT_GRAY8A;
} else {
av_log(avctx, AV_LOG_ERROR, "unsupported bit depth %d "
"and color type %d\n",
s->bit_depth, s->color_type);
goto fail;
}
if(p->data[0])
avctx->release_buffer(avctx, p);
p->reference= 3;
if(avctx->get_buffer(avctx, p) < 0){
av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
goto fail;
}
p->pict_type= AV_PICTURE_TYPE_I;
p->key_frame= 1;
p->interlaced_frame = !!s->interlace_type;
/* compute the compressed row size */
if (!s->interlace_type) {
s->crow_size = s->row_size + 1;
} else {
s->pass = 0;
s->pass_row_size = ff_png_pass_row_size(s->pass,
s->bits_per_pixel,
s->width);
s->crow_size = s->pass_row_size + 1;
}
av_dlog(avctx, "row_size=%d crow_size =%d\n",
s->row_size, s->crow_size);
s->image_buf = p->data[0];
s->image_linesize = p->linesize[0];
/* copy the palette if needed */
if (avctx->pix_fmt == PIX_FMT_PAL8)
memcpy(p->data[1], s->palette, 256 * sizeof(uint32_t));
/* empty row is used if differencing to the first row */
s->last_row = av_mallocz(s->row_size);
if (!s->last_row)
goto fail;
if (s->interlace_type ||
s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
s->tmp_row = av_malloc(s->row_size);
if (!s->tmp_row)
goto fail;
}
/* compressed row */
crow_buf_base = av_malloc(s->row_size + 16);
if (!crow_buf_base)
goto fail;
/* we want crow_buf+1 to be 16-byte aligned */
s->crow_buf = crow_buf_base + 15;
s->zstream.avail_out = s->crow_size;
s->zstream.next_out = s->crow_buf;
}
s->state |= PNG_IDAT;
if (png_decode_idat(s, length) < 0)
goto fail;
bytestream2_skip(&s->gb, 4); /* crc */
break;
case MKTAG('P', 'L', 'T', 'E'):
{
int n, i, r, g, b;
if ((length % 3) != 0 || length > 256 * 3)
goto skip_tag;
/* read the palette */
n = length / 3;
for(i=0;i<n;i++) {
r = bytestream2_get_byte(&s->gb);
g = bytestream2_get_byte(&s->gb);
b = bytestream2_get_byte(&s->gb);
s->palette[i] = (0xff << 24) | (r << 16) | (g << 8) | b;
}
for(;i<256;i++) {
s->palette[i] = (0xff << 24);
}
s->state |= PNG_PLTE;
bytestream2_skip(&s->gb, 4); /* crc */
}
break;
case MKTAG('t', 'R', 'N', 'S'):
{
int v, i;
/* read the transparency. XXX: Only palette mode supported */
if (s->color_type != PNG_COLOR_TYPE_PALETTE ||
length > 256 ||
!(s->state & PNG_PLTE))
goto skip_tag;
for(i=0;i<length;i++) {
v = bytestream2_get_byte(&s->gb);
s->palette[i] = (s->palette[i] & 0x00ffffff) | (v << 24);
}
bytestream2_skip(&s->gb, 4); /* crc */
}
break;
case MKTAG('I', 'E', 'N', 'D'):
if (!(s->state & PNG_ALLIMAGE))
av_log(avctx, AV_LOG_ERROR, "IEND without all image\n");
if (!(s->state & (PNG_ALLIMAGE|PNG_IDAT))) {
goto fail;
}
bytestream2_skip(&s->gb, 4); /* crc */
goto exit_loop;
default:
/* skip tag */
skip_tag:
bytestream2_skip(&s->gb, length + 4);
break;
}
}
exit_loop:
if(s->bits_per_pixel == 1 && s->color_type == PNG_COLOR_TYPE_PALETTE){
int i, j;
uint8_t *pd = s->current_picture->data[0];
for(j=0; j < s->height; j++) {
for(i=s->width/8-1; i>=0; i--) {
pd[8*i+7]= pd[i] &1;
pd[8*i+6]= (pd[i]>>1)&1;
pd[8*i+5]= (pd[i]>>2)&1;
pd[8*i+4]= (pd[i]>>3)&1;
pd[8*i+3]= (pd[i]>>4)&1;
pd[8*i+2]= (pd[i]>>5)&1;
pd[8*i+1]= (pd[i]>>6)&1;
pd[8*i+0]= pd[i]>>7;
}
pd += s->image_linesize;
}
}
if(s->bits_per_pixel == 2){
int i, j;
uint8_t *pd = s->current_picture->data[0];
for(j=0; j < s->height; j++) {
if (s->color_type == PNG_COLOR_TYPE_PALETTE){
for(i=s->width/4-1; i>=0; i--) {
pd[4*i+3]= pd[i] &3;
pd[4*i+2]= (pd[i]>>2)&3;
pd[4*i+1]= (pd[i]>>4)&3;
pd[4*i+0]= pd[i]>>6;
}
} else {
for(i=s->width/4-1; i>=0; i--) {
pd[4*i+3]= ( pd[i] &3)*0x55;
pd[4*i+2]= ((pd[i]>>2)&3)*0x55;
pd[4*i+1]= ((pd[i]>>4)&3)*0x55;
pd[4*i+0]= ( pd[i]>>6 )*0x55;
}
}
pd += s->image_linesize;
}
}
if(s->bits_per_pixel == 4){
int i, j;
uint8_t *pd = s->current_picture->data[0];
for(j=0; j < s->height; j++) {
if (s->color_type == PNG_COLOR_TYPE_PALETTE){
for(i=s->width/2-1; i>=0; i--) {
pd[2*i+1]= pd[i]&15;
pd[2*i+0]= pd[i]>>4;
}
} else {
for(i=s->width/2-1; i>=0; i--) {
pd[2*i+1]= (pd[i]&15)*0x11;
pd[2*i+0]= (pd[i]>>4)*0x11;
}
}
pd += s->image_linesize;
}
}
/* handle p-frames only if a predecessor frame is available */
if(s->last_picture->data[0] != NULL) {
if(!(avpkt->flags & AV_PKT_FLAG_KEY)) {
int i, j;
uint8_t *pd = s->current_picture->data[0];
uint8_t *pd_last = s->last_picture->data[0];
for(j=0; j < s->height; j++) {
for(i=0; i < s->width * s->bpp; i++) {
pd[i] += pd_last[i];
}
pd += s->image_linesize;
pd_last += s->image_linesize;
}
}
}
*picture= *s->current_picture;
*data_size = sizeof(AVFrame);
ret = bytestream2_tell(&s->gb);
the_end:
inflateEnd(&s->zstream);
av_free(crow_buf_base);
s->crow_buf = NULL;
av_freep(&s->last_row);
av_freep(&s->tmp_row);
return ret;
fail:
ret = -1;
goto the_end;
}
static av_cold int png_dec_init(AVCodecContext *avctx)
{
PNGDecContext *s = avctx->priv_data;
s->current_picture = &s->picture1;
s->last_picture = &s->picture2;
avcodec_get_frame_defaults(&s->picture1);
avcodec_get_frame_defaults(&s->picture2);
ff_pngdsp_init(&s->dsp);
return 0;
}
static av_cold int png_dec_end(AVCodecContext *avctx)
{
PNGDecContext *s = avctx->priv_data;
if (s->picture1.data[0])
avctx->release_buffer(avctx, &s->picture1);
if (s->picture2.data[0])
avctx->release_buffer(avctx, &s->picture2);
return 0;
}
AVCodec ff_png_decoder = {
.name = "png",
.type = AVMEDIA_TYPE_VIDEO,
.id = CODEC_ID_PNG,
.priv_data_size = sizeof(PNGDecContext),
.init = png_dec_init,
.close = png_dec_end,
.decode = decode_frame,
.capabilities = CODEC_CAP_DR1 /*| CODEC_CAP_DRAW_HORIZ_BAND*/,
.long_name = NULL_IF_CONFIG_SMALL("PNG (Portable Network Graphics) image"),
};
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