/*
  * 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/bprint.h"

 #include "libavutil/imgutils.h"

 #include "avcodec.h"
 #include "bytestream.h"

 #include "internal.h"

 #include "png.h"

 #include "pngdsp.h"

 
 /* TODO:

  * - add 16 bit depth support

  */
 
 #include <zlib.h>
 
 //#define DEBUG
 

 typedef struct PNGDecContext {

     PNGDSPContext dsp;

     AVCodecContext *avctx;

     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 - bpp; 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)\

     for (; i < size; i++) {\
         dst[i] = op(dst[i-bpp], src[i], last[i]);\
     }\

 /* 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 = (unsigned char *)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) {

             av_log(s->avctx, AV_LOG_ERROR, "inflate returned %d\n", ret);

             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;
         }

         if (ret == Z_STREAM_END && s->zstream.avail_in > 0) {
             av_log(NULL, AV_LOG_WARNING, "%d undecompressed bytes left in buffer\n", s->zstream.avail_in);
             return 0;
         }

     }
     return 0;
 }
 

 static int decode_zbuf(AVBPrint *bp, const uint8_t *data,
                        const uint8_t *data_end)
 {
     z_stream zstream;
     unsigned char *buf;
     unsigned buf_size;
     int ret;
 
     zstream.zalloc = ff_png_zalloc;
     zstream.zfree  = ff_png_zfree;
     zstream.opaque = NULL;
     if (inflateInit(&zstream) != Z_OK)
         return AVERROR_EXTERNAL;
     zstream.next_in  = (unsigned char *)data;
     zstream.avail_in = data_end - data;
     av_bprint_init(bp, 0, -1);
 
     while (zstream.avail_in > 0) {
         av_bprint_get_buffer(bp, 1, &buf, &buf_size);
         if (!buf_size) {
             ret = AVERROR(ENOMEM);
             goto fail;
         }
         zstream.next_out  = buf;
         zstream.avail_out = buf_size;
         ret = inflate(&zstream, Z_PARTIAL_FLUSH);
         if (ret != Z_OK && ret != Z_STREAM_END) {
             ret = AVERROR_EXTERNAL;
             goto fail;
         }
         bp->len += zstream.next_out - buf;
         if (ret == Z_STREAM_END)
             break;
     }
     inflateEnd(&zstream);
     bp->str[bp->len] = 0;
     return 0;
 
 fail:
     inflateEnd(&zstream);
     av_bprint_finalize(bp, NULL);
     return ret;
 }
 
 static uint8_t *iso88591_to_utf8(const uint8_t *in, size_t size_in)
 {
     size_t extra = 0, i;
     uint8_t *out, *q;
 
     for (i = 0; i < size_in; i++)
         extra += in[i] >= 0x80;
     if (size_in == SIZE_MAX || extra > SIZE_MAX - size_in - 1)
         return NULL;
     q = out = av_malloc(size_in + extra + 1);
     if (!out)
         return NULL;
     for (i = 0; i < size_in; i++) {
         if (in[i] >= 0x80) {
             *(q++) = 0xC0 | (in[i] >> 6);
             *(q++) = 0x80 | (in[i] & 0x3F);
         } else {
             *(q++) = in[i];
         }
     }
     *(q++) = 0;
     return out;
 }
 
 static int decode_text_chunk(PNGDecContext *s, uint32_t length, int compressed,
                              AVDictionary **dict)
 {
     int ret, method;
     const uint8_t *data        = s->gb.buffer;
     const uint8_t *data_end    = data + length;
     const uint8_t *keyword     = data;
     const uint8_t *keyword_end = memchr(keyword, 0, data_end - keyword);
     uint8_t *kw_utf8 = NULL, *text, *txt_utf8 = NULL;
     unsigned text_len;
     AVBPrint bp;
 
     if (!keyword_end)
         return AVERROR_INVALIDDATA;
     data = keyword_end + 1;
 
     if (compressed) {
         if (data == data_end)
             return AVERROR_INVALIDDATA;
         method = *(data++);
         if (method)
             return AVERROR_INVALIDDATA;
         if ((ret = decode_zbuf(&bp, data, data_end)) < 0)
             return ret;
         text_len = bp.len;
         av_bprint_finalize(&bp, (char **)&text);
         if (!text)
             return AVERROR(ENOMEM);
     } else {
         text = (uint8_t *)data;
         text_len = data_end - text;
     }
 
     kw_utf8  = iso88591_to_utf8(keyword, keyword_end - keyword);
     txt_utf8 = iso88591_to_utf8(text, text_len);
     if (text != data)
         av_free(text);
     if (!(kw_utf8 && txt_utf8)) {
         av_free(kw_utf8);
         av_free(txt_utf8);
         return AVERROR(ENOMEM);
     }
 
     av_dict_set(dict, kw_utf8, txt_utf8,
                 AV_DICT_DONT_STRDUP_KEY | AV_DICT_DONT_STRDUP_VAL);
     return 0;
 }
 

 static int decode_frame(AVCodecContext *avctx,

                         void *data, int *got_frame,

                         AVPacket *avpkt)

 {

     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;

     PNGDecContext * const s = avctx->priv_data;

     AVFrame *picture = data;

     AVFrame *p;

     AVDictionary *metadata = NULL;

     uint8_t *crow_buf_base = NULL;

     uint32_t tag, length;

     int64_t sig;

     int ret;

     FFSWAP(AVFrame *, s->current_picture, s->last_picture);
     avctx->coded_frame= s->current_picture;
     p = s->current_picture;
 

     bytestream2_init(&s->gb, buf, buf_size);
 

     /* check signature */

     sig = bytestream2_get_be64(&s->gb);
     if (sig != PNGSIG &&
         sig != MNGSIG) {

         av_log(avctx, AV_LOG_ERROR, "Missing png signature\n");

         return -1;

     }

     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) {
         av_log(avctx, AV_LOG_ERROR, "inflateInit returned %d\n", ret);

         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('p', 'H', 'Y', 's'):
             if (s->state & PNG_IDAT) {
                 av_log(avctx, AV_LOG_ERROR, "pHYs after IDAT\n");
                 goto fail;
             }
             avctx->sample_aspect_ratio.num = bytestream2_get_be32(&s->gb);
             avctx->sample_aspect_ratio.den = bytestream2_get_be32(&s->gb);
             if (avctx->sample_aspect_ratio.num < 0 || avctx->sample_aspect_ratio.den < 0)
                 avctx->sample_aspect_ratio = (AVRational){ 0, 1 };
             bytestream2_skip(&s->gb, 1); /* unit specifier */
             bytestream2_skip(&s->gb, 4); /* crc */
             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 = AV_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 = AV_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 = AV_PIX_FMT_GRAY8;

                 } else if (s->bit_depth == 16 &&
                            s->color_type == PNG_COLOR_TYPE_GRAY) {

                     avctx->pix_fmt = AV_PIX_FMT_GRAY16BE;

                 } else if (s->bit_depth == 16 &&
                            s->color_type == PNG_COLOR_TYPE_RGB) {

                     avctx->pix_fmt = AV_PIX_FMT_RGB48BE;

                 } else if (s->bit_depth == 16 &&
                            s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {

                     avctx->pix_fmt = AV_PIX_FMT_RGBA64BE;

                 } else if ((s->bits_per_pixel == 1 || s->bits_per_pixel == 2 || s->bits_per_pixel == 4 || s->bits_per_pixel == 8) &&
                            s->color_type == PNG_COLOR_TYPE_PALETTE) {

                     avctx->pix_fmt = AV_PIX_FMT_PAL8;

                 } else if (s->bit_depth == 1) {

                     avctx->pix_fmt = AV_PIX_FMT_MONOBLACK;

                 } else if (s->bit_depth == 8 &&
                            s->color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {

                     avctx->pix_fmt = AV_PIX_FMT_Y400A;

                 } 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(ff_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 == AV_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] = (0xFFU << 24) | (r << 16) | (g << 8) | b;

                 }
                 for(;i<256;i++) {

                     s->palette[i] = (0xFFU << 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('t', 'E', 'X', 't'):
             if (decode_text_chunk(s, length, 0, &metadata) < 0)
                 av_log(avctx, AV_LOG_WARNING, "Broken tEXt chunk\n");
             bytestream2_skip(&s->gb, length + 4);
             break;
         case MKTAG('z', 'T', 'X', 't'):
             if (decode_text_chunk(s, length, 1, &metadata) < 0)
                 av_log(avctx, AV_LOG_WARNING, "Broken zTXt chunk\n");
             bytestream2_skip(&s->gb, length + 4);
             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++) {

             i = s->width/4;

             if (s->color_type == PNG_COLOR_TYPE_PALETTE){

                 if ((s->width&3) >= 3) pd[4*i+2]= (pd[i]>>2)&3;
                 if ((s->width&3) >= 2) pd[4*i+1]= (pd[i]>>4)&3;
                 if ((s->width&3) >= 1) pd[4*i+0]=  pd[i]>>6;
                 for(i--; 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 {

                 if ((s->width&3) >= 3) pd[4*i+2]= ((pd[i]>>2)&3)*0x55;
                 if ((s->width&3) >= 2) pd[4*i+1]= ((pd[i]>>4)&3)*0x55;
                 if ((s->width&3) >= 1) pd[4*i+0]= ( pd[i]>>6   )*0x55;
                 for(i--; 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++) {

             i=s->width/2;

             if (s->color_type == PNG_COLOR_TYPE_PALETTE){

                 if (s->width&1) pd[2*i+0]= pd[i]>>4;
                 for(i--; i>=0; i--) {

                 pd[2*i+1]= pd[i]&15;
                 pd[2*i+0]= pd[i]>>4;
             }

             } else {

                 if (s->width&1) pd[2*i+0]= (pd[i]>>4)*0x11;
                 for(i--; 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)
             && s->last_picture->width == s->current_picture->width
             && s->last_picture->height== s->current_picture->height

             && s->last_picture->format== s->current_picture->format

          ) {

             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;
             }
         }
     }
 

     s->current_picture->metadata = metadata;
     metadata = NULL;

     *picture= *s->current_picture;

     *got_frame = 1;

     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:

     av_dict_free(&metadata);

     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);

     s->avctx = avctx;
 

     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             = AV_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"),

 };