libavcodec/pngdec.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 "png.h"
 #include "dsputil.h"

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

 #include <zlib.h>

 //#define DEBUG

 typedef struct PNGDecContext {
     DSPContext dsp;

     const uint8_t *bytestream;
     const uint8_t *bytestream_start;
     const uint8_t *bytestream_end;
     AVFrame 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 y pixels can be written in a pass */
 static const uint8_t png_pass_dsp_ymask[NB_PASSES] = {
     0xff, 0xff, 0x0f, 0xcc, 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 = ff_png_pass_mask[pass];
     dsp_mask = png_pass_dsp_mask[pass];
     switch(bits_per_pixel) {
     case 1:
         /* we must initialize the line to zero before writing to it */
         if (pass == 0)
             memset(dst, 0, (width + 7) >> 3);
         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] |= b << (7 - j);
             }
             if ((mask << j) & 0x80)
                 src_x++;
         }
         break;
     default:
         bpp = bits_per_pixel >> 3;
         d = dst;
         s = src;
         if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
             for(x = 0; x < width; x++) {
                 j = x & 7;
                 if ((dsp_mask << j) & 0x80) {
                     *(uint32_t *)d = (s[3] << 24) | (s[0] << 16) | (s[1] << 8) | s[2];
                 }
                 d += bpp;
                 if ((mask << j) & 0x80)
                     s += bpp;
             }
         } else {
             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)\

 /* NOTE: 'dst' can be equal to 'last' */
 static void png_filter_row(DSPContext *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 > 1 && 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_png_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;
     }
 }

 static av_always_inline void convert_to_rgb32_loco(uint8_t *dst, const uint8_t *src, int width, int loco)
 {
     int j;
     unsigned int r, g, b, a;

     for(j = 0;j < width; j++) {
         r = src[0];
         g = src[1];
         b = src[2];
         a = src[3];
         if(loco) {
             r = (r+g)&0xff;
             b = (b+g)&0xff;
         }
         *(uint32_t *)dst = (a << 24) | (r << 16) | (g << 8) | b;
         dst += 4;
         src += 4;
     }
 }

 static void convert_to_rgb32(uint8_t *dst, const uint8_t *src, int width, int loco)
 {
     if(loco)
         convert_to_rgb32_loco(dst, src, width, 1);
     else
         convert_to_rgb32_loco(dst, src, width, 0);
 }

 static void deloco_rgb24(uint8_t *dst, int size)
 {
     int i;
     for(i=0; i<size; i+=3) {
         int g = dst[i+1];
         dst[i+0] += g;
         dst[i+2] += g;
     }
 }

 /* 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;
         /* need to swap bytes correctly for RGB_ALPHA */
         if (s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
             png_filter_row(&s->dsp, s->tmp_row, s->crow_buf[0], s->crow_buf + 1,
                            s->last_row, s->row_size, s->bpp);
             convert_to_rgb32(ptr, s->tmp_row, s->width, s->filter_type == PNG_FILTER_TYPE_LOCO);
             FFSWAP(uint8_t*, s->last_row, s->tmp_row);
         } else {
             /* in normal case, we avoid one copy */
             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->color_type == PNG_COLOR_TYPE_RGB && s->y > 0)
             deloco_rgb24(ptr - s->image_linesize, s->row_size);
         s->y++;
         if (s->y == s->height) {
             s->state |= PNG_ALLIMAGE;
             if (s->filter_type == PNG_FILTER_TYPE_LOCO &&
                 s->color_type == PNG_COLOR_TYPE_RGB)
                 deloco_rgb24(ptr, s->row_size);
         }
     } 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) {
                 /* NOTE: RGB32 is handled directly in png_put_interlaced_row */
                 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) {
                 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 = length;
     s->zstream.next_in = s->bytestream;
     s->bytestream += length;

     if(s->bytestream > s->bytestream_end)
         return -1;

     /* 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,
                         const uint8_t *buf, int buf_size)
 {
     PNGDecContext * const s = avctx->priv_data;
     AVFrame *picture = data;
     AVFrame * const p= &s->picture;
     uint32_t tag, length;
     int ret, crc;

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

     /* check signature */
     if (memcmp(s->bytestream, ff_pngsig, 8) != 0 &&
         memcmp(s->bytestream, ff_mngsig, 8) != 0)
         return -1;
     s->bytestream+= 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(;;) {
         int tag32;
         if (s->bytestream >= s->bytestream_end)
             goto fail;
         length = bytestream_get_be32(&s->bytestream);
         if (length > 0x7fffffff)
             goto fail;
         tag32 = bytestream_get_be32(&s->bytestream);
         tag = bswap_32(tag32);
 #ifdef DEBUG
         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);
 #endif
         switch(tag) {
         case MKTAG('I', 'H', 'D', 'R'):
             if (length != 13)
                 goto fail;
             s->width = bytestream_get_be32(&s->bytestream);
             s->height = bytestream_get_be32(&s->bytestream);
             if(avcodec_check_dimensions(avctx, s->width, s->height)){
                 s->width= s->height= 0;
                 goto fail;
             }
             s->bit_depth = *s->bytestream++;
             s->color_type = *s->bytestream++;
             s->compression_type = *s->bytestream++;
             s->filter_type = *s->bytestream++;
             s->interlace_type = *s->bytestream++;
             crc = bytestream_get_be32(&s->bytestream);
             s->state |= PNG_IHDR;
 #ifdef DEBUG
             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);
 #endif
             break;
         case MKTAG('I', 'D', 'A', 'T'):
             if (!(s->state & PNG_IHDR))
                 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 == 8 &&
                     s->color_type == PNG_COLOR_TYPE_RGB) {
                     avctx->pix_fmt = PIX_FMT_RGB24;
                 } else if (s->bit_depth == 8 &&
                            s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
                     avctx->pix_fmt = PIX_FMT_RGB32;
                 } else if (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 == 1 &&
                            s->color_type == PNG_COLOR_TYPE_GRAY) {
                     avctx->pix_fmt = PIX_FMT_MONOBLACK;
                 } else if (s->bit_depth == 8 &&
                            s->color_type == PNG_COLOR_TYPE_PALETTE) {
                     avctx->pix_fmt = PIX_FMT_PAL8;
                 } else {
                     goto fail;
                 }
                 if(p->data[0])
                     avctx->release_buffer(avctx, p);

                 p->reference= 0;
                 if(avctx->get_buffer(avctx, p) < 0){
                     av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
                     goto fail;
                 }
                 p->pict_type= FF_I_TYPE;
                 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;
                 }
 #ifdef DEBUG
                 av_log(avctx, AV_LOG_DEBUG, "row_size=%d crow_size =%d\n",
                        s->row_size, s->crow_size);
 #endif
                 s->image_buf = p->data[0];
                 s->image_linesize = p->linesize[0];
                 /* copy the palette if needed */
                 if (s->color_type == PNG_COLOR_TYPE_PALETTE)
                     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 */
                 s->crow_buf = av_malloc(s->row_size + 1);
                 if (!s->crow_buf)
                     goto fail;
                 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;
             /* skip crc */
             crc = bytestream_get_be32(&s->bytestream);
             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 = *s->bytestream++;
                     g = *s->bytestream++;
                     b = *s->bytestream++;
                     s->palette[i] = (0xff << 24) | (r << 16) | (g << 8) | b;
                 }
                 for(;i<256;i++) {
                     s->palette[i] = (0xff << 24);
                 }
                 s->state |= PNG_PLTE;
                 crc = bytestream_get_be32(&s->bytestream);
             }
             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 = *s->bytestream++;
                     s->palette[i] = (s->palette[i] & 0x00ffffff) | (v << 24);
                 }
                 crc = bytestream_get_be32(&s->bytestream);
             }
             break;
         case MKTAG('I', 'E', 'N', 'D'):
             if (!(s->state & PNG_ALLIMAGE))
                 goto fail;
             crc = bytestream_get_be32(&s->bytestream);
             goto exit_loop;
         default:
             /* skip tag */
         skip_tag:
             s->bytestream += length + 4;
             break;
         }
     }
  exit_loop:
     *picture= s->picture;
     *data_size = sizeof(AVFrame);

     ret = s->bytestream - s->bytestream_start;
  the_end:
     inflateEnd(&s->zstream);
     av_freep(&s->crow_buf);
     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;

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

     return 0;
 }

 AVCodec png_decoder = {
     "png",
     CODEC_TYPE_VIDEO,
     CODEC_ID_PNG,
     sizeof(PNGDecContext),
     png_dec_init,
     NULL,
     NULL, //decode_end,
     decode_frame,
     0 /*CODEC_CAP_DR1*/ /*| CODEC_CAP_DRAW_HORIZ_BAND*/,
     NULL,
     .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 "png.h"
	#include "dsputil.h"

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

	#include <zlib.h>

	//#define DEBUG

	typedef struct PNGDecContext {
	DSPContext dsp;

	const uint8_t *bytestream;
	const uint8_t *bytestream_start;
	const uint8_t *bytestream_end;
	AVFrame 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 y pixels can be written in a pass */
	static const uint8_t png_pass_dsp_ymask[NB_PASSES] = {
	0xff, 0xff, 0x0f, 0xcc, 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 = ff_png_pass_mask[pass];
	dsp_mask = png_pass_dsp_mask[pass];
	switch(bits_per_pixel) {
	case 1:
	/* we must initialize the line to zero before writing to it */
	if (pass == 0)
	memset(dst, 0, (width + 7) >> 3);
	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] \|= b << (7 - j);
	}
	if ((mask << j) & 0x80)
	src_x++;
	}
	break;
	default:
	bpp = bits_per_pixel >> 3;
	d = dst;
	s = src;
	if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
	for(x = 0; x < width; x++) {
	j = x & 7;
	if ((dsp_mask << j) & 0x80) {
	(uint32_t )d = (s[3] << 24) \| (s[0] << 16) \| (s[1] << 8) \| s[2];
	}
	d += bpp;
	if ((mask << j) & 0x80)
	s += bpp;
	}
	} else {
	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)\

	/* NOTE: 'dst' can be equal to 'last' */
	static void png_filter_row(DSPContext 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 > 1 && 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_png_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;
	}
	}

	static av_always_inline void convert_to_rgb32_loco(uint8_t dst, const uint8_t src, int width, int loco)
	{
	int j;
	unsigned int r, g, b, a;

	for(j = 0;j < width; j++) {
	r = src[0];
	g = src[1];
	b = src[2];
	a = src[3];
	if(loco) {
	r = (r+g)&0xff;
	b = (b+g)&0xff;
	}
	(uint32_t )dst = (a << 24) \| (r << 16) \| (g << 8) \| b;
	dst += 4;
	src += 4;
	}
	}

	static void convert_to_rgb32(uint8_t dst, const uint8_t src, int width, int loco)
	{
	if(loco)
	convert_to_rgb32_loco(dst, src, width, 1);
	else
	convert_to_rgb32_loco(dst, src, width, 0);
	}

	static void deloco_rgb24(uint8_t *dst, int size)
	{
	int i;
	for(i=0; i<size; i+=3) {
	int g = dst[i+1];
	dst[i+0] += g;
	dst[i+2] += g;
	}
	}

	/* 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;
	/* need to swap bytes correctly for RGB_ALPHA */
	if (s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
	png_filter_row(&s->dsp, s->tmp_row, s->crow_buf[0], s->crow_buf + 1,
	s->last_row, s->row_size, s->bpp);
	convert_to_rgb32(ptr, s->tmp_row, s->width, s->filter_type == PNG_FILTER_TYPE_LOCO);
	FFSWAP(uint8_t*, s->last_row, s->tmp_row);
	} else {
	/* in normal case, we avoid one copy */
	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->color_type == PNG_COLOR_TYPE_RGB && s->y > 0)
	deloco_rgb24(ptr - s->image_linesize, s->row_size);
	s->y++;
	if (s->y == s->height) {
	s->state \|= PNG_ALLIMAGE;
	if (s->filter_type == PNG_FILTER_TYPE_LOCO &&
	s->color_type == PNG_COLOR_TYPE_RGB)
	deloco_rgb24(ptr, s->row_size);
	}
	} 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) {
	/* NOTE: RGB32 is handled directly in png_put_interlaced_row */
	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) {
	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 = length;
	s->zstream.next_in = s->bytestream;
	s->bytestream += length;

	if(s->bytestream > s->bytestream_end)
	return -1;

	/* 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,
	const uint8_t *buf, int buf_size)
	{
	PNGDecContext * const s = avctx->priv_data;
	AVFrame *picture = data;
	AVFrame * const p= &s->picture;
	uint32_t tag, length;
	int ret, crc;

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

	/* check signature */
	if (memcmp(s->bytestream, ff_pngsig, 8) != 0 &&
	memcmp(s->bytestream, ff_mngsig, 8) != 0)
	return -1;
	s->bytestream+= 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(;;) {
	int tag32;
	if (s->bytestream >= s->bytestream_end)
	goto fail;
	length = bytestream_get_be32(&s->bytestream);
	if (length > 0x7fffffff)
	goto fail;
	tag32 = bytestream_get_be32(&s->bytestream);
	tag = bswap_32(tag32);
	#ifdef DEBUG
	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);
	#endif
	switch(tag) {
	case MKTAG('I', 'H', 'D', 'R'):
	if (length != 13)
	goto fail;
	s->width = bytestream_get_be32(&s->bytestream);
	s->height = bytestream_get_be32(&s->bytestream);
	if(avcodec_check_dimensions(avctx, s->width, s->height)){
	s->width= s->height= 0;
	goto fail;
	}
	s->bit_depth = *s->bytestream++;
	s->color_type = *s->bytestream++;
	s->compression_type = *s->bytestream++;
	s->filter_type = *s->bytestream++;
	s->interlace_type = *s->bytestream++;
	crc = bytestream_get_be32(&s->bytestream);
	s->state \|= PNG_IHDR;
	#ifdef DEBUG
	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);
	#endif
	break;
	case MKTAG('I', 'D', 'A', 'T'):
	if (!(s->state & PNG_IHDR))
	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 == 8 &&
	s->color_type == PNG_COLOR_TYPE_RGB) {
	avctx->pix_fmt = PIX_FMT_RGB24;
	} else if (s->bit_depth == 8 &&
	s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
	avctx->pix_fmt = PIX_FMT_RGB32;
	} else if (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 == 1 &&
	s->color_type == PNG_COLOR_TYPE_GRAY) {
	avctx->pix_fmt = PIX_FMT_MONOBLACK;
	} else if (s->bit_depth == 8 &&
	s->color_type == PNG_COLOR_TYPE_PALETTE) {
	avctx->pix_fmt = PIX_FMT_PAL8;
	} else {
	goto fail;
	}
	if(p->data[0])
	avctx->release_buffer(avctx, p);

	p->reference= 0;
	if(avctx->get_buffer(avctx, p) < 0){
	av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
	goto fail;
	}
	p->pict_type= FF_I_TYPE;
	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;
	}
	#ifdef DEBUG
	av_log(avctx, AV_LOG_DEBUG, "row_size=%d crow_size =%d\n",
	s->row_size, s->crow_size);
	#endif
	s->image_buf = p->data[0];
	s->image_linesize = p->linesize[0];
	/* copy the palette if needed */
	if (s->color_type == PNG_COLOR_TYPE_PALETTE)
	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 */
	s->crow_buf = av_malloc(s->row_size + 1);
	if (!s->crow_buf)
	goto fail;
	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;
	/* skip crc */
	crc = bytestream_get_be32(&s->bytestream);
	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 = *s->bytestream++;
	g = *s->bytestream++;
	b = *s->bytestream++;
	s->palette[i] = (0xff << 24) \| (r << 16) \| (g << 8) \| b;
	}
	for(;i<256;i++) {
	s->palette[i] = (0xff << 24);
	}
	s->state \|= PNG_PLTE;
	crc = bytestream_get_be32(&s->bytestream);
	}
	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 = *s->bytestream++;
	s->palette[i] = (s->palette[i] & 0x00ffffff) \| (v << 24);
	}
	crc = bytestream_get_be32(&s->bytestream);
	}
	break;
	case MKTAG('I', 'E', 'N', 'D'):
	if (!(s->state & PNG_ALLIMAGE))
	goto fail;
	crc = bytestream_get_be32(&s->bytestream);
	goto exit_loop;
	default:
	/* skip tag */
	skip_tag:
	s->bytestream += length + 4;
	break;
	}
	}
	exit_loop:
	*picture= s->picture;
	*data_size = sizeof(AVFrame);

	ret = s->bytestream - s->bytestream_start;
	the_end:
	inflateEnd(&s->zstream);
	av_freep(&s->crow_buf);
	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;

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

	return 0;
	}

	AVCodec png_decoder = {
	"png",
	CODEC_TYPE_VIDEO,
	CODEC_ID_PNG,
	sizeof(PNGDecContext),
	png_dec_init,
	NULL,
	NULL, //decode_end,
	decode_frame,
	0 /CODEC_CAP_DR1/ /\| CODEC_CAP_DRAW_HORIZ_BAND/,
	NULL,
	.long_name = NULL_IF_CONFIG_SMALL("PNG image"),
	};