libavcodec/pngenc.c - vendor/opensource/ffmpeg - Git at Google

 /*
  * 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 "avcodec.h"
 #include "bytestream.h"
 #include "dsputil.h"
 #include "png.h"

 /* TODO:
  * - add 2, 4 and 16 bit depth support
  */

 #include <zlib.h>

 //#define DEBUG

 #define IOBUF_SIZE 4096

 typedef struct PNGEncContext {
     DSPContext dsp;

     uint8_t *bytestream;
     uint8_t *bytestream_start;
     uint8_t *bytestream_end;
     AVFrame picture;

     int filter_type;

     z_stream zstream;
     uint8_t buf[IOBUF_SIZE];
 } PNGEncContext;

 static void png_get_interlaced_row(uint8_t *dst, int row_size,
                                    int bits_per_pixel, int pass,
                                    const uint8_t *src, int width)
 {
     int x, mask, dst_x, j, b, bpp;
     uint8_t *d;
     const uint8_t *s;

     mask = ff_png_pass_mask[pass];
     switch(bits_per_pixel) {
     case 1:
         memset(dst, 0, row_size);
         dst_x = 0;
         for(x = 0; x < width; x++) {
             j = (x & 7);
             if ((mask << j) & 0x80) {
                 b = (src[x >> 3] >> (7 - j)) & 1;
                 dst[dst_x >> 3] |= b << (7 - (dst_x & 7));
                 dst_x++;
             }
         }
         break;
     default:
         bpp = bits_per_pixel >> 3;
         d = dst;
         s = src;
         for(x = 0; x < width; x++) {
             j = x & 7;
             if ((mask << j) & 0x80) {
                 memcpy(d, s, bpp);
                 d += bpp;
             }
             s += bpp;
         }
         break;
     }
 }

 static void sub_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 = src[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] = src[i] - p;
     }
 }

 static void png_filter_row(DSPContext *dsp, uint8_t *dst, int filter_type,
                            uint8_t *src, uint8_t *top, int size, int bpp)
 {
     int i;

     switch(filter_type) {
     case PNG_FILTER_VALUE_NONE:
         memcpy(dst, src, size);
         break;
     case PNG_FILTER_VALUE_SUB:
         dsp->diff_bytes(dst, src, src-bpp, size);
         memcpy(dst, src, bpp);
         break;
     case PNG_FILTER_VALUE_UP:
         dsp->diff_bytes(dst, src, top, size);
         break;
     case PNG_FILTER_VALUE_AVG:
         for(i = 0; i < bpp; i++)
             dst[i] = src[i] - (top[i] >> 1);
         for(; i < size; i++)
             dst[i] = src[i] - ((src[i-bpp] + top[i]) >> 1);
         break;
     case PNG_FILTER_VALUE_PAETH:
         for(i = 0; i < bpp; i++)
             dst[i] = src[i] - top[i];
         sub_png_paeth_prediction(dst+i, src+i, top+i, size-i, bpp);
         break;
     }
 }

 static uint8_t *png_choose_filter(PNGEncContext *s, uint8_t *dst,
                                   uint8_t *src, uint8_t *top, int size, int bpp)
 {
     int pred = s->filter_type;
     assert(bpp || !pred);
     if(!top && pred)
         pred = PNG_FILTER_VALUE_SUB;
     if(pred == PNG_FILTER_VALUE_MIXED) {
         int i;
         int cost, bcost = INT_MAX;
         uint8_t *buf1 = dst, *buf2 = dst + size + 16;
         for(pred=0; pred<5; pred++) {
             png_filter_row(&s->dsp, buf1+1, pred, src, top, size, bpp);
             buf1[0] = pred;
             cost = 0;
             for(i=0; i<=size; i++)
                 cost += abs((int8_t)buf1[i]);
             if(cost < bcost) {
                 bcost = cost;
                 FFSWAP(uint8_t*, buf1, buf2);
             }
         }
         return buf2;
     } else {
         png_filter_row(&s->dsp, dst+1, pred, src, top, size, bpp);
         dst[0] = pred;
         return dst;
     }
 }

 static void convert_from_rgb32(uint8_t *dst, const uint8_t *src, int width)
 {
     uint8_t *d;
     int j;
     unsigned int v;

     d = dst;
     for(j = 0; j < width; j++) {
         v = ((const uint32_t *)src)[j];
         d[0] = v >> 16;
         d[1] = v >> 8;
         d[2] = v;
         d[3] = v >> 24;
         d += 4;
     }
 }

 static void png_write_chunk(uint8_t **f, uint32_t tag,
                             const uint8_t *buf, int length)
 {
     uint32_t crc;
     uint8_t tagbuf[4];

     bytestream_put_be32(f, length);
     crc = crc32(0, Z_NULL, 0);
     AV_WL32(tagbuf, tag);
     crc = crc32(crc, tagbuf, 4);
     bytestream_put_be32(f, bswap_32(tag));
     if (length > 0) {
         crc = crc32(crc, buf, length);
         memcpy(*f, buf, length);
         *f += length;
     }
     bytestream_put_be32(f, crc);
 }

 /* XXX: do filtering */
 static int png_write_row(PNGEncContext *s, const uint8_t *data, int size)
 {
     int ret;

     s->zstream.avail_in = size;
     s->zstream.next_in = (uint8_t *)data;
     while (s->zstream.avail_in > 0) {
         ret = deflate(&s->zstream, Z_NO_FLUSH);
         if (ret != Z_OK)
             return -1;
         if (s->zstream.avail_out == 0) {
             if(s->bytestream_end - s->bytestream > IOBUF_SIZE + 100)
                 png_write_chunk(&s->bytestream, MKTAG('I', 'D', 'A', 'T'), s->buf, IOBUF_SIZE);
             s->zstream.avail_out = IOBUF_SIZE;
             s->zstream.next_out = s->buf;
         }
     }
     return 0;
 }

 static int encode_frame(AVCodecContext *avctx, unsigned char *buf, int buf_size, void *data){
     PNGEncContext *s = avctx->priv_data;
     AVFrame *pict = data;
     AVFrame * const p= &s->picture;
     int bit_depth, color_type, y, len, row_size, ret, is_progressive;
     int bits_per_pixel, pass_row_size;
     int compression_level;
     uint8_t *ptr, *top;
     uint8_t *crow_base = NULL, *crow_buf, *crow;
     uint8_t *progressive_buf = NULL;
     uint8_t *rgba_buf = NULL;
     uint8_t *top_buf = NULL;

     *p = *pict;
     p->pict_type= FF_I_TYPE;
     p->key_frame= 1;

     s->bytestream_start=
     s->bytestream= buf;
     s->bytestream_end= buf+buf_size;

     is_progressive = !!(avctx->flags & CODEC_FLAG_INTERLACED_DCT);
     switch(avctx->pix_fmt) {
     case PIX_FMT_RGB32:
         bit_depth = 8;
         color_type = PNG_COLOR_TYPE_RGB_ALPHA;
         break;
     case PIX_FMT_RGB24:
         bit_depth = 8;
         color_type = PNG_COLOR_TYPE_RGB;
         break;
     case PIX_FMT_GRAY8:
         bit_depth = 8;
         color_type = PNG_COLOR_TYPE_GRAY;
         break;
     case PIX_FMT_MONOBLACK:
         bit_depth = 1;
         color_type = PNG_COLOR_TYPE_GRAY;
         break;
     case PIX_FMT_PAL8:
         bit_depth = 8;
         color_type = PNG_COLOR_TYPE_PALETTE;
         break;
     default:
         return -1;
     }
     bits_per_pixel = ff_png_get_nb_channels(color_type) * bit_depth;
     row_size = (avctx->width * bits_per_pixel + 7) >> 3;

     s->zstream.zalloc = ff_png_zalloc;
     s->zstream.zfree = ff_png_zfree;
     s->zstream.opaque = NULL;
     compression_level = avctx->compression_level == FF_COMPRESSION_DEFAULT ?
                             Z_DEFAULT_COMPRESSION :
                             av_clip(avctx->compression_level, 0, 9);
     ret = deflateInit2(&s->zstream, compression_level,
                        Z_DEFLATED, 15, 8, Z_DEFAULT_STRATEGY);
     if (ret != Z_OK)
         return -1;
     crow_base = av_malloc((row_size + 32) << (s->filter_type == PNG_FILTER_VALUE_MIXED));
     if (!crow_base)
         goto fail;
     crow_buf = crow_base + 15; // pixel data should be aligned, but there's a control byte before it
     if (is_progressive) {
         progressive_buf = av_malloc(row_size + 1);
         if (!progressive_buf)
             goto fail;
     }
     if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
         rgba_buf = av_malloc(row_size + 1);
         if (!rgba_buf)
             goto fail;
     }
     if (is_progressive || color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
         top_buf = av_malloc(row_size + 1);
         if (!top_buf)
             goto fail;
     }

     /* write png header */
     memcpy(s->bytestream, ff_pngsig, 8);
     s->bytestream += 8;

     AV_WB32(s->buf, avctx->width);
     AV_WB32(s->buf + 4, avctx->height);
     s->buf[8] = bit_depth;
     s->buf[9] = color_type;
     s->buf[10] = 0; /* compression type */
     s->buf[11] = 0; /* filter type */
     s->buf[12] = is_progressive; /* interlace type */

     png_write_chunk(&s->bytestream, MKTAG('I', 'H', 'D', 'R'), s->buf, 13);

     /* put the palette if needed */
     if (color_type == PNG_COLOR_TYPE_PALETTE) {
         int has_alpha, alpha, i;
         unsigned int v;
         uint32_t *palette;
         uint8_t *alpha_ptr;

         palette = (uint32_t *)p->data[1];
         ptr = s->buf;
         alpha_ptr = s->buf + 256 * 3;
         has_alpha = 0;
         for(i = 0; i < 256; i++) {
             v = palette[i];
             alpha = v >> 24;
             if (alpha && alpha != 0xff)
                 has_alpha = 1;
             *alpha_ptr++ = alpha;
             bytestream_put_be24(&ptr, v);
         }
         png_write_chunk(&s->bytestream, MKTAG('P', 'L', 'T', 'E'), s->buf, 256 * 3);
         if (has_alpha) {
             png_write_chunk(&s->bytestream, MKTAG('t', 'R', 'N', 'S'), s->buf + 256 * 3, 256);
         }
     }

     /* now put each row */
     s->zstream.avail_out = IOBUF_SIZE;
     s->zstream.next_out = s->buf;
     if (is_progressive) {
         int pass;

         for(pass = 0; pass < NB_PASSES; pass++) {
             /* NOTE: a pass is completely omited if no pixels would be
                output */
             pass_row_size = ff_png_pass_row_size(pass, bits_per_pixel, avctx->width);
             if (pass_row_size > 0) {
                 top = NULL;
                 for(y = 0; y < avctx->height; y++) {
                     if ((ff_png_pass_ymask[pass] << (y & 7)) & 0x80) {
                         ptr = p->data[0] + y * p->linesize[0];
                         FFSWAP(uint8_t*, progressive_buf, top_buf);
                         if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
                             convert_from_rgb32(rgba_buf, ptr, avctx->width);
                             ptr = rgba_buf;
                         }
                         png_get_interlaced_row(progressive_buf, pass_row_size,
                                                bits_per_pixel, pass,
                                                ptr, avctx->width);
                         crow = png_choose_filter(s, crow_buf, progressive_buf, top, pass_row_size, bits_per_pixel>>3);
                         png_write_row(s, crow, pass_row_size + 1);
                         top = progressive_buf;
                     }
                 }
             }
         }
     } else {
         top = NULL;
         for(y = 0; y < avctx->height; y++) {
             ptr = p->data[0] + y * p->linesize[0];
             if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
                 FFSWAP(uint8_t*, rgba_buf, top_buf);
                 convert_from_rgb32(rgba_buf, ptr, avctx->width);
                 ptr = rgba_buf;
             }
             crow = png_choose_filter(s, crow_buf, ptr, top, row_size, bits_per_pixel>>3);
             png_write_row(s, crow, row_size + 1);
             top = ptr;
         }
     }
     /* compress last bytes */
     for(;;) {
         ret = deflate(&s->zstream, Z_FINISH);
         if (ret == Z_OK || ret == Z_STREAM_END) {
             len = IOBUF_SIZE - s->zstream.avail_out;
             if (len > 0 && s->bytestream_end - s->bytestream > len + 100) {
                 png_write_chunk(&s->bytestream, MKTAG('I', 'D', 'A', 'T'), s->buf, len);
             }
             s->zstream.avail_out = IOBUF_SIZE;
             s->zstream.next_out = s->buf;
             if (ret == Z_STREAM_END)
                 break;
         } else {
             goto fail;
         }
     }
     png_write_chunk(&s->bytestream, MKTAG('I', 'E', 'N', 'D'), NULL, 0);

     ret = s->bytestream - s->bytestream_start;
  the_end:
     av_free(crow_base);
     av_free(progressive_buf);
     av_free(rgba_buf);
     av_free(top_buf);
     deflateEnd(&s->zstream);
     return ret;
  fail:
     ret = -1;
     goto the_end;
 }

 static av_cold int png_enc_init(AVCodecContext *avctx){
     PNGEncContext *s = avctx->priv_data;

     avcodec_get_frame_defaults(&s->picture);
     avctx->coded_frame= &s->picture;
     dsputil_init(&s->dsp, avctx);

     s->filter_type = av_clip(avctx->prediction_method, PNG_FILTER_VALUE_NONE, PNG_FILTER_VALUE_MIXED);
     if(avctx->pix_fmt == PIX_FMT_MONOBLACK)
         s->filter_type = PNG_FILTER_VALUE_NONE;

     return 0;
 }

 AVCodec png_encoder = {
     "png",
     CODEC_TYPE_VIDEO,
     CODEC_ID_PNG,
     sizeof(PNGEncContext),
     png_enc_init,
     encode_frame,
     NULL, //encode_end,
     .pix_fmts= (enum PixelFormat[]){PIX_FMT_RGB24, PIX_FMT_RGB32, PIX_FMT_PAL8, PIX_FMT_GRAY8, PIX_FMT_MONOBLACK, PIX_FMT_NONE},
     .long_name= NULL_IF_CONFIG_SMALL("PNG image"),
 };
	/*
	* 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 "avcodec.h"
	#include "bytestream.h"
	#include "dsputil.h"
	#include "png.h"

	/* TODO:
	* - add 2, 4 and 16 bit depth support
	*/

	#include <zlib.h>

	//#define DEBUG

	#define IOBUF_SIZE 4096

	typedef struct PNGEncContext {
	DSPContext dsp;

	uint8_t *bytestream;
	uint8_t *bytestream_start;
	uint8_t *bytestream_end;
	AVFrame picture;

	int filter_type;

	z_stream zstream;
	uint8_t buf[IOBUF_SIZE];
	} PNGEncContext;

	static void png_get_interlaced_row(uint8_t *dst, int row_size,
	int bits_per_pixel, int pass,
	const uint8_t *src, int width)
	{
	int x, mask, dst_x, j, b, bpp;
	uint8_t *d;
	const uint8_t *s;

	mask = ff_png_pass_mask[pass];
	switch(bits_per_pixel) {
	case 1:
	memset(dst, 0, row_size);
	dst_x = 0;
	for(x = 0; x < width; x++) {
	j = (x & 7);
	if ((mask << j) & 0x80) {
	b = (src[x >> 3] >> (7 - j)) & 1;
	dst[dst_x >> 3] \|= b << (7 - (dst_x & 7));
	dst_x++;
	}
	}
	break;
	default:
	bpp = bits_per_pixel >> 3;
	d = dst;
	s = src;
	for(x = 0; x < width; x++) {
	j = x & 7;
	if ((mask << j) & 0x80) {
	memcpy(d, s, bpp);
	d += bpp;
	}
	s += bpp;
	}
	break;
	}
	}

	static void sub_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 = src[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] = src[i] - p;
	}
	}

	static void png_filter_row(DSPContext dsp, uint8_t dst, int filter_type,
	uint8_t src, uint8_t top, int size, int bpp)
	{
	int i;

	switch(filter_type) {
	case PNG_FILTER_VALUE_NONE:
	memcpy(dst, src, size);
	break;
	case PNG_FILTER_VALUE_SUB:
	dsp->diff_bytes(dst, src, src-bpp, size);
	memcpy(dst, src, bpp);
	break;
	case PNG_FILTER_VALUE_UP:
	dsp->diff_bytes(dst, src, top, size);
	break;
	case PNG_FILTER_VALUE_AVG:
	for(i = 0; i < bpp; i++)
	dst[i] = src[i] - (top[i] >> 1);
	for(; i < size; i++)
	dst[i] = src[i] - ((src[i-bpp] + top[i]) >> 1);
	break;
	case PNG_FILTER_VALUE_PAETH:
	for(i = 0; i < bpp; i++)
	dst[i] = src[i] - top[i];
	sub_png_paeth_prediction(dst+i, src+i, top+i, size-i, bpp);
	break;
	}
	}

	static uint8_t png_choose_filter(PNGEncContext s, uint8_t *dst,
	uint8_t src, uint8_t top, int size, int bpp)
	{
	int pred = s->filter_type;
	assert(bpp \|\| !pred);
	if(!top && pred)
	pred = PNG_FILTER_VALUE_SUB;
	if(pred == PNG_FILTER_VALUE_MIXED) {
	int i;
	int cost, bcost = INT_MAX;
	uint8_t buf1 = dst, buf2 = dst + size + 16;
	for(pred=0; pred<5; pred++) {
	png_filter_row(&s->dsp, buf1+1, pred, src, top, size, bpp);
	buf1[0] = pred;
	cost = 0;
	for(i=0; i<=size; i++)
	cost += abs((int8_t)buf1[i]);
	if(cost < bcost) {
	bcost = cost;
	FFSWAP(uint8_t*, buf1, buf2);
	}
	}
	return buf2;
	} else {
	png_filter_row(&s->dsp, dst+1, pred, src, top, size, bpp);
	dst[0] = pred;
	return dst;
	}
	}

	static void convert_from_rgb32(uint8_t dst, const uint8_t src, int width)
	{
	uint8_t *d;
	int j;
	unsigned int v;

	d = dst;
	for(j = 0; j < width; j++) {
	v = ((const uint32_t *)src)[j];
	d[0] = v >> 16;
	d[1] = v >> 8;
	d[2] = v;
	d[3] = v >> 24;
	d += 4;
	}
	}

	static void png_write_chunk(uint8_t **f, uint32_t tag,
	const uint8_t *buf, int length)
	{
	uint32_t crc;
	uint8_t tagbuf[4];

	bytestream_put_be32(f, length);
	crc = crc32(0, Z_NULL, 0);
	AV_WL32(tagbuf, tag);
	crc = crc32(crc, tagbuf, 4);
	bytestream_put_be32(f, bswap_32(tag));
	if (length > 0) {
	crc = crc32(crc, buf, length);
	memcpy(*f, buf, length);
	*f += length;
	}
	bytestream_put_be32(f, crc);
	}

	/* XXX: do filtering */
	static int png_write_row(PNGEncContext s, const uint8_t data, int size)
	{
	int ret;

	s->zstream.avail_in = size;
	s->zstream.next_in = (uint8_t *)data;
	while (s->zstream.avail_in > 0) {
	ret = deflate(&s->zstream, Z_NO_FLUSH);
	if (ret != Z_OK)
	return -1;
	if (s->zstream.avail_out == 0) {
	if(s->bytestream_end - s->bytestream > IOBUF_SIZE + 100)
	png_write_chunk(&s->bytestream, MKTAG('I', 'D', 'A', 'T'), s->buf, IOBUF_SIZE);
	s->zstream.avail_out = IOBUF_SIZE;
	s->zstream.next_out = s->buf;
	}
	}
	return 0;
	}

	static int encode_frame(AVCodecContext avctx, unsigned char buf, int buf_size, void *data){
	PNGEncContext *s = avctx->priv_data;
	AVFrame *pict = data;
	AVFrame * const p= &s->picture;
	int bit_depth, color_type, y, len, row_size, ret, is_progressive;
	int bits_per_pixel, pass_row_size;
	int compression_level;
	uint8_t ptr, top;
	uint8_t crow_base = NULL, crow_buf, *crow;
	uint8_t *progressive_buf = NULL;
	uint8_t *rgba_buf = NULL;
	uint8_t *top_buf = NULL;

	p = pict;
	p->pict_type= FF_I_TYPE;
	p->key_frame= 1;

	s->bytestream_start=
	s->bytestream= buf;
	s->bytestream_end= buf+buf_size;

	is_progressive = !!(avctx->flags & CODEC_FLAG_INTERLACED_DCT);
	switch(avctx->pix_fmt) {
	case PIX_FMT_RGB32:
	bit_depth = 8;
	color_type = PNG_COLOR_TYPE_RGB_ALPHA;
	break;
	case PIX_FMT_RGB24:
	bit_depth = 8;
	color_type = PNG_COLOR_TYPE_RGB;
	break;
	case PIX_FMT_GRAY8:
	bit_depth = 8;
	color_type = PNG_COLOR_TYPE_GRAY;
	break;
	case PIX_FMT_MONOBLACK:
	bit_depth = 1;
	color_type = PNG_COLOR_TYPE_GRAY;
	break;
	case PIX_FMT_PAL8:
	bit_depth = 8;
	color_type = PNG_COLOR_TYPE_PALETTE;
	break;
	default:
	return -1;
	}
	bits_per_pixel = ff_png_get_nb_channels(color_type) * bit_depth;
	row_size = (avctx->width * bits_per_pixel + 7) >> 3;

	s->zstream.zalloc = ff_png_zalloc;
	s->zstream.zfree = ff_png_zfree;
	s->zstream.opaque = NULL;
	compression_level = avctx->compression_level == FF_COMPRESSION_DEFAULT ?
	Z_DEFAULT_COMPRESSION :
	av_clip(avctx->compression_level, 0, 9);
	ret = deflateInit2(&s->zstream, compression_level,
	Z_DEFLATED, 15, 8, Z_DEFAULT_STRATEGY);
	if (ret != Z_OK)
	return -1;
	crow_base = av_malloc((row_size + 32) << (s->filter_type == PNG_FILTER_VALUE_MIXED));
	if (!crow_base)
	goto fail;
	crow_buf = crow_base + 15; // pixel data should be aligned, but there's a control byte before it
	if (is_progressive) {
	progressive_buf = av_malloc(row_size + 1);
	if (!progressive_buf)
	goto fail;
	}
	if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
	rgba_buf = av_malloc(row_size + 1);
	if (!rgba_buf)
	goto fail;
	}
	if (is_progressive \|\| color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
	top_buf = av_malloc(row_size + 1);
	if (!top_buf)
	goto fail;
	}

	/* write png header */
	memcpy(s->bytestream, ff_pngsig, 8);
	s->bytestream += 8;

	AV_WB32(s->buf, avctx->width);
	AV_WB32(s->buf + 4, avctx->height);
	s->buf[8] = bit_depth;
	s->buf[9] = color_type;
	s->buf[10] = 0; /* compression type */
	s->buf[11] = 0; /* filter type */
	s->buf[12] = is_progressive; /* interlace type */

	png_write_chunk(&s->bytestream, MKTAG('I', 'H', 'D', 'R'), s->buf, 13);

	/* put the palette if needed */
	if (color_type == PNG_COLOR_TYPE_PALETTE) {
	int has_alpha, alpha, i;
	unsigned int v;
	uint32_t *palette;
	uint8_t *alpha_ptr;

	palette = (uint32_t *)p->data[1];
	ptr = s->buf;
	alpha_ptr = s->buf + 256 * 3;
	has_alpha = 0;
	for(i = 0; i < 256; i++) {
	v = palette[i];
	alpha = v >> 24;
	if (alpha && alpha != 0xff)
	has_alpha = 1;
	*alpha_ptr++ = alpha;
	bytestream_put_be24(&ptr, v);
	}
	png_write_chunk(&s->bytestream, MKTAG('P', 'L', 'T', 'E'), s->buf, 256 * 3);
	if (has_alpha) {
	png_write_chunk(&s->bytestream, MKTAG('t', 'R', 'N', 'S'), s->buf + 256 * 3, 256);
	}
	}

	/* now put each row */
	s->zstream.avail_out = IOBUF_SIZE;
	s->zstream.next_out = s->buf;
	if (is_progressive) {
	int pass;

	for(pass = 0; pass < NB_PASSES; pass++) {
	/* NOTE: a pass is completely omited if no pixels would be
	output */
	pass_row_size = ff_png_pass_row_size(pass, bits_per_pixel, avctx->width);
	if (pass_row_size > 0) {
	top = NULL;
	for(y = 0; y < avctx->height; y++) {
	if ((ff_png_pass_ymask[pass] << (y & 7)) & 0x80) {
	ptr = p->data[0] + y * p->linesize[0];
	FFSWAP(uint8_t*, progressive_buf, top_buf);
	if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
	convert_from_rgb32(rgba_buf, ptr, avctx->width);
	ptr = rgba_buf;
	}
	png_get_interlaced_row(progressive_buf, pass_row_size,
	bits_per_pixel, pass,
	ptr, avctx->width);
	crow = png_choose_filter(s, crow_buf, progressive_buf, top, pass_row_size, bits_per_pixel>>3);
	png_write_row(s, crow, pass_row_size + 1);
	top = progressive_buf;
	}
	}
	}
	}
	} else {
	top = NULL;
	for(y = 0; y < avctx->height; y++) {
	ptr = p->data[0] + y * p->linesize[0];
	if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
	FFSWAP(uint8_t*, rgba_buf, top_buf);
	convert_from_rgb32(rgba_buf, ptr, avctx->width);
	ptr = rgba_buf;
	}
	crow = png_choose_filter(s, crow_buf, ptr, top, row_size, bits_per_pixel>>3);
	png_write_row(s, crow, row_size + 1);
	top = ptr;
	}
	}
	/* compress last bytes */
	for(;;) {
	ret = deflate(&s->zstream, Z_FINISH);
	if (ret == Z_OK \|\| ret == Z_STREAM_END) {
	len = IOBUF_SIZE - s->zstream.avail_out;
	if (len > 0 && s->bytestream_end - s->bytestream > len + 100) {
	png_write_chunk(&s->bytestream, MKTAG('I', 'D', 'A', 'T'), s->buf, len);
	}
	s->zstream.avail_out = IOBUF_SIZE;
	s->zstream.next_out = s->buf;
	if (ret == Z_STREAM_END)
	break;
	} else {
	goto fail;
	}
	}
	png_write_chunk(&s->bytestream, MKTAG('I', 'E', 'N', 'D'), NULL, 0);

	ret = s->bytestream - s->bytestream_start;
	the_end:
	av_free(crow_base);
	av_free(progressive_buf);
	av_free(rgba_buf);
	av_free(top_buf);
	deflateEnd(&s->zstream);
	return ret;
	fail:
	ret = -1;
	goto the_end;
	}

	static av_cold int png_enc_init(AVCodecContext *avctx){
	PNGEncContext *s = avctx->priv_data;

	avcodec_get_frame_defaults(&s->picture);
	avctx->coded_frame= &s->picture;
	dsputil_init(&s->dsp, avctx);

	s->filter_type = av_clip(avctx->prediction_method, PNG_FILTER_VALUE_NONE, PNG_FILTER_VALUE_MIXED);
	if(avctx->pix_fmt == PIX_FMT_MONOBLACK)
	s->filter_type = PNG_FILTER_VALUE_NONE;

	return 0;
	}

	AVCodec png_encoder = {
	"png",
	CODEC_TYPE_VIDEO,
	CODEC_ID_PNG,
	sizeof(PNGEncContext),
	png_enc_init,
	encode_frame,
	NULL, //encode_end,
	.pix_fmts= (enum PixelFormat[]){PIX_FMT_RGB24, PIX_FMT_RGB32, PIX_FMT_PAL8, PIX_FMT_GRAY8, PIX_FMT_MONOBLACK, PIX_FMT_NONE},
	.long_name= NULL_IF_CONFIG_SMALL("PNG image"),
	};