/*
  * 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/avassert.h"

 #include "libavutil/bprint.h"

 #include "libavutil/imgutils.h"

 #include "libavutil/stereo3d.h"

 #include "libavutil/mastering_display_metadata.h"

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

 #include "internal.h"

 #include "apng.h"

 #include "png.h"

 #include "pngdsp.h"

 #include "thread.h"

 
 #include <zlib.h>
 

 enum PNGHeaderState {
     PNG_IHDR = 1 << 0,
     PNG_PLTE = 1 << 1,
 };
 
 enum PNGImageState {
     PNG_IDAT     = 1 << 0,
     PNG_ALLIMAGE = 1 << 1,
 };
 

 typedef struct PNGDecContext {

     PNGDSPContext dsp;

     AVCodecContext *avctx;

     GetByteContext gb;

     ThreadFrame previous_picture;

     ThreadFrame last_picture;
     ThreadFrame picture;

     enum PNGHeaderState hdr_state;
     enum PNGImageState pic_state;

     int width, height;

     int cur_w, cur_h;

     int last_w, last_h;

     int x_offset, y_offset;

     int last_x_offset, last_y_offset;

     uint8_t dispose_op, blend_op;

     uint8_t last_dispose_op;

     int bit_depth;
     int color_type;
     int compression_type;
     int interlace_type;
     int filter_type;
     int channels;
     int bits_per_pixel;
     int bpp;

     int has_trns;

     uint8_t transparent_color_be[6];

 
     uint8_t *image_buf;
     int image_linesize;
     uint32_t palette[256];
     uint8_t *crow_buf;
     uint8_t *last_row;

     unsigned int last_row_size;

     uint8_t *tmp_row;

     unsigned int tmp_row_size;

     uint8_t *buffer;
     int buffer_size;

     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) {

                 unsigned 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 & 3) ? size - 3 : size;
 

             if (w > i) {

                 dsp->add_paeth_prediction(dst + i, src + i, last + i, size - 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 + s->y_offset) + s->x_offset * s->bpp;

         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->cur_h) {

             s->pic_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 + s->y_offset) + s->x_offset * s->bpp;

             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);

                 FFSWAP(unsigned int, s->last_row_size, s->tmp_row_size);

                 got_line = 1;
             }
             if ((png_pass_dsp_ymask[s->pass] << (s->y & 7)) & 0x80) {

                 png_put_interlaced_row(ptr, s->cur_w, s->bits_per_pixel, s->pass,

                                        s->color_type, s->last_row);
             }
             s->y++;

             if (s->y == s->cur_h) {

                 memset(s->last_row, 0, s->row_size);

                 for (;;) {

                     if (s->pass == NB_PASSES - 1) {

                         s->pic_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->cur_w);

                         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 error %d\n", ret);
             return AVERROR_EXTERNAL;

         }
         if (s->zstream.avail_out == 0) {

             if (!(s->pic_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, 2, &buf, &buf_size);
         if (buf_size < 2) {

             ret = AVERROR(ENOMEM);
             goto fail;
         }
         zstream.next_out  = buf;

         zstream.avail_out = buf_size - 1;

         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;

         ret = av_bprint_finalize(&bp, (char **)&text);
         if (ret < 0)
             return ret;

     } 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_ihdr_chunk(AVCodecContext *avctx, PNGDecContext *s,
                              uint32_t length)
 {
     if (length != 13)
         return AVERROR_INVALIDDATA;

     if (s->pic_state & PNG_IDAT) {

         av_log(avctx, AV_LOG_ERROR, "IHDR after IDAT\n");
         return AVERROR_INVALIDDATA;
     }
 

     if (s->hdr_state & PNG_IHDR) {

         av_log(avctx, AV_LOG_ERROR, "Multiple IHDR\n");
         return AVERROR_INVALIDDATA;
     }
 

     s->width  = s->cur_w = bytestream2_get_be32(&s->gb);
     s->height = s->cur_h = bytestream2_get_be32(&s->gb);

     if (av_image_check_size(s->width, s->height, 0, avctx)) {

         s->cur_w = s->cur_h = s->width = s->height = 0;

         av_log(avctx, AV_LOG_ERROR, "Invalid image size\n");
         return AVERROR_INVALIDDATA;
     }
     s->bit_depth        = bytestream2_get_byte(&s->gb);

     if (s->bit_depth != 1 && s->bit_depth != 2 && s->bit_depth != 4 &&
         s->bit_depth != 8 && s->bit_depth != 16) {
         av_log(avctx, AV_LOG_ERROR, "Invalid bit depth\n");
         goto error;
     }

     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->hdr_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);

 
     return 0;

 error:
     s->cur_w = s->cur_h = s->width = s->height = 0;
     s->bit_depth = 8;
     return AVERROR_INVALIDDATA;

 }
 
 static int decode_phys_chunk(AVCodecContext *avctx, PNGDecContext *s)
 {

     if (s->pic_state & PNG_IDAT) {

         av_log(avctx, AV_LOG_ERROR, "pHYs after IDAT\n");
         return AVERROR_INVALIDDATA;
     }
     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 */
 

     return 0;
 }
 

 static int decode_idat_chunk(AVCodecContext *avctx, PNGDecContext *s,
                              uint32_t length, AVFrame *p)
 {
     int ret;

     size_t byte_depth = s->bit_depth > 8 ? 2 : 1;

     if (!(s->hdr_state & PNG_IHDR)) {

         av_log(avctx, AV_LOG_ERROR, "IDAT without IHDR\n");
         return AVERROR_INVALIDDATA;
     }

     if (!(s->pic_state & PNG_IDAT)) {

         /* init image info */

         ret = ff_set_dimensions(avctx, s->width, s->height);
         if (ret < 0)
             return ret;

 
         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       = (s->cur_w * 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 && s->bits_per_pixel == 1 && avctx->codec_id != AV_CODEC_ID_APNG) {

             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_YA8;
         } else if (s->bit_depth == 16 &&
                 s->color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
             avctx->pix_fmt = AV_PIX_FMT_YA16BE;
         } else {

             avpriv_report_missing_feature(avctx,
                                           "Bit depth %d color type %d",
                                           s->bit_depth, s->color_type);
             return AVERROR_PATCHWELCOME;

         }
 

         if (s->has_trns && s->color_type != PNG_COLOR_TYPE_PALETTE) {
             switch (avctx->pix_fmt) {
             case AV_PIX_FMT_RGB24:
                 avctx->pix_fmt = AV_PIX_FMT_RGBA;
                 break;
 
             case AV_PIX_FMT_RGB48BE:
                 avctx->pix_fmt = AV_PIX_FMT_RGBA64BE;
                 break;
 
             case AV_PIX_FMT_GRAY8:
                 avctx->pix_fmt = AV_PIX_FMT_YA8;
                 break;
 
             case AV_PIX_FMT_GRAY16BE:
                 avctx->pix_fmt = AV_PIX_FMT_YA16BE;
                 break;
 
             default:

                 avpriv_request_sample(avctx, "bit depth %d "
                         "and color type %d with TRNS",
                         s->bit_depth, s->color_type);
                 return AVERROR_INVALIDDATA;

             }
 
             s->bpp += byte_depth;
         }
 

         if ((ret = ff_thread_get_buffer(avctx, &s->picture, AV_GET_BUFFER_FLAG_REF)) < 0)
             return ret;

         if (avctx->codec_id == AV_CODEC_ID_APNG && s->last_dispose_op != APNG_DISPOSE_OP_PREVIOUS) {
             ff_thread_release_buffer(avctx, &s->previous_picture);
             if ((ret = ff_thread_get_buffer(avctx, &s->previous_picture, AV_GET_BUFFER_FLAG_REF)) < 0)
                 return ret;
         }

         p->pict_type        = AV_PICTURE_TYPE_I;
         p->key_frame        = 1;
         p->interlaced_frame = !!s->interlace_type;
 

         ff_thread_finish_setup(avctx);
 

         /* 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->cur_w);

             s->crow_size = s->pass_row_size + 1;
         }

         ff_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 */
         av_fast_padded_mallocz(&s->last_row, &s->last_row_size, s->row_size);
         if (!s->last_row)
             return AVERROR_INVALIDDATA;
         if (s->interlace_type ||
                 s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
             av_fast_padded_malloc(&s->tmp_row, &s->tmp_row_size, s->row_size);
             if (!s->tmp_row)
                 return AVERROR_INVALIDDATA;
         }
         /* compressed row */
         av_fast_padded_malloc(&s->buffer, &s->buffer_size, s->row_size + 16);
         if (!s->buffer)
             return AVERROR(ENOMEM);
 
         /* we want crow_buf+1 to be 16-byte aligned */
         s->crow_buf          = s->buffer + 15;
         s->zstream.avail_out = s->crow_size;
         s->zstream.next_out  = s->crow_buf;
     }

     s->pic_state |= PNG_IDAT;

 
     /* set image to non-transparent bpp while decompressing */
     if (s->has_trns && s->color_type != PNG_COLOR_TYPE_PALETTE)
         s->bpp -= byte_depth;
 
     ret = png_decode_idat(s, length);
 
     if (s->has_trns && s->color_type != PNG_COLOR_TYPE_PALETTE)
         s->bpp += byte_depth;
 
     if (ret < 0)

         return ret;

     bytestream2_skip(&s->gb, 4); /* crc */
 
     return 0;
 }
 

 static int decode_plte_chunk(AVCodecContext *avctx, PNGDecContext *s,
                              uint32_t length)
 {
     int n, i, r, g, b;
 
     if ((length % 3) != 0 || length > 256 * 3)
         return AVERROR_INVALIDDATA;
     /* 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->hdr_state |= PNG_PLTE;

     bytestream2_skip(&s->gb, 4);     /* crc */
 
     return 0;
 }
 

 static int decode_trns_chunk(AVCodecContext *avctx, PNGDecContext *s,
                              uint32_t length)
 {
     int v, i;
 

     if (!(s->hdr_state & PNG_IHDR)) {

         av_log(avctx, AV_LOG_ERROR, "trns before IHDR\n");
         return AVERROR_INVALIDDATA;
     }
 

     if (s->pic_state & PNG_IDAT) {

         av_log(avctx, AV_LOG_ERROR, "trns after IDAT\n");
         return AVERROR_INVALIDDATA;
     }
 

     if (s->color_type == PNG_COLOR_TYPE_PALETTE) {

         if (length > 256 || !(s->hdr_state & PNG_PLTE))

             return AVERROR_INVALIDDATA;
 
         for (i = 0; i < length; i++) {

             unsigned v = bytestream2_get_byte(&s->gb);

             s->palette[i] = (s->palette[i] & 0x00ffffff) | (v << 24);
         }
     } else if (s->color_type == PNG_COLOR_TYPE_GRAY || s->color_type == PNG_COLOR_TYPE_RGB) {
         if ((s->color_type == PNG_COLOR_TYPE_GRAY && length != 2) ||

             (s->color_type == PNG_COLOR_TYPE_RGB && length != 6) ||
             s->bit_depth == 1)

             return AVERROR_INVALIDDATA;
 
         for (i = 0; i < length / 2; i++) {
             /* only use the least significant bits */

             v = av_mod_uintp2(bytestream2_get_be16(&s->gb), s->bit_depth);

 
             if (s->bit_depth > 8)
                 AV_WB16(&s->transparent_color_be[2 * i], v);
             else
                 s->transparent_color_be[i] = v;
         }
     } else {

         return AVERROR_INVALIDDATA;
     }
 

     bytestream2_skip(&s->gb, 4); /* crc */

     s->has_trns = 1;
 

     return 0;
 }
 

 static int decode_iccp_chunk(PNGDecContext *s, int length, AVFrame *f)
 {
     int ret, cnt = 0;
     uint8_t *data, profile_name[82];
     AVBPrint bp;
     AVFrameSideData *sd;
 
     while ((profile_name[cnt++] = bytestream2_get_byte(&s->gb)) && cnt < 81);
     if (cnt > 80) {
         av_log(s->avctx, AV_LOG_ERROR, "iCCP with invalid name!\n");
         return AVERROR_INVALIDDATA;
     }
 
     length = FFMAX(length - cnt, 0);
 
     if (bytestream2_get_byte(&s->gb) != 0) {
         av_log(s->avctx, AV_LOG_ERROR, "iCCP with invalid compression!\n");
         return AVERROR_INVALIDDATA;
     }
 
     length = FFMAX(length - 1, 0);
 

     if ((ret = decode_zbuf(&bp, s->gb.buffer, s->gb.buffer + length)) < 0)

         return ret;
 

     ret = av_bprint_finalize(&bp, (char **)&data);
     if (ret < 0)
         return ret;

     sd = av_frame_new_side_data(f, AV_FRAME_DATA_ICC_PROFILE, bp.len);
     if (!sd) {
         av_free(data);

         return AVERROR(ENOMEM);

     }

 
     av_dict_set(&sd->metadata, "name", profile_name, 0);
     memcpy(sd->data, data, bp.len);
     av_free(data);
 
     /* ICC compressed data and CRC */
     bytestream2_skip(&s->gb, length + 4);
 
     return 0;
 }
 

 static void handle_small_bpp(PNGDecContext *s, AVFrame *p)
 {
     if (s->bits_per_pixel == 1 && s->color_type == PNG_COLOR_TYPE_PALETTE) {
         int i, j, k;
         uint8_t *pd = p->data[0];
         for (j = 0; j < s->height; j++) {
             i = s->width / 8;
             for (k = 7; k >= 1; k--)
                 if ((s->width&7) >= k)
                     pd[8*i + k - 1] = (pd[i]>>8-k) & 1;
             for (i--; 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;
         }
     } else if (s->bits_per_pixel == 2) {
         int i, j;
         uint8_t *pd = p->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;
         }
     } else if (s->bits_per_pixel == 4) {
         int i, j;
         uint8_t *pd = p->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;
         }
     }
 }
 

 static int decode_fctl_chunk(AVCodecContext *avctx, PNGDecContext *s,
                              uint32_t length)
 {

     uint32_t sequence_number;

     int cur_w, cur_h, x_offset, y_offset, dispose_op, blend_op;

 
     if (length != 26)
         return AVERROR_INVALIDDATA;
 

     if (!(s->hdr_state & PNG_IHDR)) {

         av_log(avctx, AV_LOG_ERROR, "fctl before IHDR\n");
         return AVERROR_INVALIDDATA;
     }
 

     s->last_w = s->cur_w;
     s->last_h = s->cur_h;
     s->last_x_offset = s->x_offset;
     s->last_y_offset = s->y_offset;
     s->last_dispose_op = s->dispose_op;
 

     sequence_number = bytestream2_get_be32(&s->gb);

     cur_w           = bytestream2_get_be32(&s->gb);
     cur_h           = bytestream2_get_be32(&s->gb);
     x_offset        = bytestream2_get_be32(&s->gb);
     y_offset        = bytestream2_get_be32(&s->gb);

     bytestream2_skip(&s->gb, 4); /* delay_num (2), delay_den (2) */

     dispose_op      = bytestream2_get_byte(&s->gb);
     blend_op        = bytestream2_get_byte(&s->gb);

     bytestream2_skip(&s->gb, 4); /* crc */
 
     if (sequence_number == 0 &&

         (cur_w != s->width ||
          cur_h != s->height ||
          x_offset != 0 ||
          y_offset != 0) ||
         cur_w <= 0 || cur_h <= 0 ||
         x_offset < 0 || y_offset < 0 ||
         cur_w > s->width - x_offset|| cur_h > s->height - y_offset)

             return AVERROR_INVALIDDATA;

     if (blend_op != APNG_BLEND_OP_OVER && blend_op != APNG_BLEND_OP_SOURCE) {
         av_log(avctx, AV_LOG_ERROR, "Invalid blend_op %d\n", blend_op);
         return AVERROR_INVALIDDATA;
     }
 

     if ((sequence_number == 0 || !s->previous_picture.f->data[0]) &&
         dispose_op == APNG_DISPOSE_OP_PREVIOUS) {

         // No previous frame to revert to for the first frame
         // Spec says to just treat it as a APNG_DISPOSE_OP_BACKGROUND

         dispose_op = APNG_DISPOSE_OP_BACKGROUND;

     }
 

     if (blend_op == APNG_BLEND_OP_OVER && !s->has_trns && (

             avctx->pix_fmt == AV_PIX_FMT_RGB24 ||
             avctx->pix_fmt == AV_PIX_FMT_RGB48BE ||
             avctx->pix_fmt == AV_PIX_FMT_PAL8 ||
             avctx->pix_fmt == AV_PIX_FMT_GRAY8 ||
             avctx->pix_fmt == AV_PIX_FMT_GRAY16BE ||
             avctx->pix_fmt == AV_PIX_FMT_MONOBLACK
         )) {

         // APNG_BLEND_OP_OVER is the same as APNG_BLEND_OP_SOURCE when there is no alpha channel
         blend_op = APNG_BLEND_OP_SOURCE;

     }
 

     s->cur_w      = cur_w;
     s->cur_h      = cur_h;
     s->x_offset   = x_offset;
     s->y_offset   = y_offset;
     s->dispose_op = dispose_op;
     s->blend_op   = blend_op;
 

     return 0;
 }
 

 static void handle_p_frame_png(PNGDecContext *s, AVFrame *p)
 {
     int i, j;
     uint8_t *pd      = p->data[0];
     uint8_t *pd_last = s->last_picture.f->data[0];
     int ls = FFMIN(av_image_get_linesize(p->format, s->width, 0), s->width * s->bpp);
 
     ff_thread_await_progress(&s->last_picture, INT_MAX, 0);
     for (j = 0; j < s->height; j++) {
         for (i = 0; i < ls; i++)
             pd[i] += pd_last[i];
         pd      += s->image_linesize;
         pd_last += s->image_linesize;
     }
 }
 

 // divide by 255 and round to nearest
 // apply a fast variant: (X+127)/255 = ((X+127)*257+257)>>16 = ((X+128)*257)>>16
 #define FAST_DIV255(x) ((((x) + 128) * 257) >> 16)
 
 static int handle_p_frame_apng(AVCodecContext *avctx, PNGDecContext *s,
                                AVFrame *p)
 {

     size_t x, y;

     uint8_t *buffer;

     if (s->blend_op == APNG_BLEND_OP_OVER &&

         avctx->pix_fmt != AV_PIX_FMT_RGBA &&

         avctx->pix_fmt != AV_PIX_FMT_GRAY8A &&
         avctx->pix_fmt != AV_PIX_FMT_PAL8) {

         avpriv_request_sample(avctx, "Blending with pixel format %s",
                               av_get_pix_fmt_name(avctx->pix_fmt));
         return AVERROR_PATCHWELCOME;
     }
 

     buffer = av_malloc_array(s->image_linesize, s->height);

     if (!buffer)
         return AVERROR(ENOMEM);
 
 

     // Do the disposal operation specified by the last frame on the frame

     if (s->last_dispose_op != APNG_DISPOSE_OP_PREVIOUS) {
         ff_thread_await_progress(&s->last_picture, INT_MAX, 0);
         memcpy(buffer, s->last_picture.f->data[0], s->image_linesize * s->height);
 
         if (s->last_dispose_op == APNG_DISPOSE_OP_BACKGROUND)
             for (y = s->last_y_offset; y < s->last_y_offset + s->last_h; ++y)
                 memset(buffer + s->image_linesize * y + s->bpp * s->last_x_offset, 0, s->bpp * s->last_w);
 
         memcpy(s->previous_picture.f->data[0], buffer, s->image_linesize * s->height);
         ff_thread_report_progress(&s->previous_picture, INT_MAX, 0);
     } else {

         ff_thread_await_progress(&s->previous_picture, INT_MAX, 0);

         memcpy(buffer, s->previous_picture.f->data[0], s->image_linesize * s->height);

     }
 

     // Perform blending
     if (s->blend_op == APNG_BLEND_OP_SOURCE) {
         for (y = s->y_offset; y < s->y_offset + s->cur_h; ++y) {
             size_t row_start = s->image_linesize * y + s->bpp * s->x_offset;
             memcpy(buffer + row_start, p->data[0] + row_start, s->bpp * s->cur_w);

         }

     } else { // APNG_BLEND_OP_OVER
         for (y = s->y_offset; y < s->y_offset + s->cur_h; ++y) {
             uint8_t *foreground = p->data[0] + s->image_linesize * y + s->bpp * s->x_offset;
             uint8_t *background = buffer + s->image_linesize * y + s->bpp * s->x_offset;
             for (x = s->x_offset; x < s->x_offset + s->cur_w; ++x, foreground += s->bpp, background += s->bpp) {
                 size_t b;
                 uint8_t foreground_alpha, background_alpha, output_alpha;

                 uint8_t output[10];

 
                 // Since we might be blending alpha onto alpha, we use the following equations:
                 // output_alpha = foreground_alpha + (1 - foreground_alpha) * background_alpha
                 // output = (foreground_alpha * foreground + (1 - foreground_alpha) * background_alpha * background) / output_alpha
 
                 switch (avctx->pix_fmt) {
                 case AV_PIX_FMT_RGBA:
                     foreground_alpha = foreground[3];
                     background_alpha = background[3];

                     break;

 
                 case AV_PIX_FMT_GRAY8A:
                     foreground_alpha = foreground[1];
                     background_alpha = background[1];
                     break;

 
                 case AV_PIX_FMT_PAL8:
                     foreground_alpha = s->palette[foreground[0]] >> 24;
                     background_alpha = s->palette[background[0]] >> 24;
                     break;

                 }

 
                 if (foreground_alpha == 0)
                     continue;
 
                 if (foreground_alpha == 255) {
                     memcpy(background, foreground, s->bpp);
                     continue;
                 }
 

                 if (avctx->pix_fmt == AV_PIX_FMT_PAL8) {
                     // TODO: Alpha blending with PAL8 will likely need the entire image converted over to RGBA first
                     avpriv_request_sample(avctx, "Alpha blending palette samples");
                     background[0] = foreground[0];
                     continue;
                 }
 

                 output_alpha = foreground_alpha + FAST_DIV255((255 - foreground_alpha) * background_alpha);
 

                 av_assert0(s->bpp <= 10);
 

                 for (b = 0; b < s->bpp - 1; ++b) {
                     if (output_alpha == 0) {
                         output[b] = 0;
                     } else if (background_alpha == 255) {
                         output[b] = FAST_DIV255(foreground_alpha * foreground[b] + (255 - foreground_alpha) * background[b]);
                     } else {
                         output[b] = (255 * foreground_alpha * foreground[b] + (255 - foreground_alpha) * background_alpha * background[b]) / (255 * output_alpha);
                     }
                 }
                 output[b] = output_alpha;
                 memcpy(background, output, s->bpp);

             }

         }

     }

     // Copy blended buffer into the frame and free
     memcpy(p->data[0], buffer, s->image_linesize * s->height);
     av_free(buffer);

 
     return 0;
 }
 

 static int decode_frame_common(AVCodecContext *avctx, PNGDecContext *s,
                                AVFrame *p, AVPacket *avpkt)

 {

     AVDictionary **metadatap = NULL;

     uint32_t tag, length;

     int decode_next_dat = 0;

     int i, ret;

     for (;;) {

         length = bytestream2_get_bytes_left(&s->gb);
         if (length <= 0) {

 
             if (avctx->codec_id == AV_CODEC_ID_PNG &&
                 avctx->skip_frame == AVDISCARD_ALL) {
                 return 0;
             }
 

             if (CONFIG_APNG_DECODER && avctx->codec_id == AV_CODEC_ID_APNG && length == 0) {

                 if (!(s->pic_state & PNG_IDAT))

                     return 0;
                 else
                     goto exit_loop;
             }
             av_log(avctx, AV_LOG_ERROR, "%d bytes left\n", length);

             if (   s->pic_state & PNG_ALLIMAGE

                 && avctx->strict_std_compliance <= FF_COMPLIANCE_NORMAL)
                 goto exit_loop;

             ret = AVERROR_INVALIDDATA;

             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");

             ret = AVERROR_INVALIDDATA;

             goto fail;

         }

         tag = bytestream2_get_le32(&s->gb);

         if (avctx->debug & FF_DEBUG_STARTCODE)

             av_log(avctx, AV_LOG_DEBUG, "png: tag=%s length=%u\n",
                    av_fourcc2str(tag), length);

 
         if (avctx->codec_id == AV_CODEC_ID_PNG &&
             avctx->skip_frame == AVDISCARD_ALL) {
             switch(tag) {
             case MKTAG('I', 'H', 'D', 'R'):
             case MKTAG('p', 'H', 'Y', 's'):
             case MKTAG('t', 'E', 'X', 't'):
             case MKTAG('I', 'D', 'A', 'T'):

             case MKTAG('t', 'R', 'N', 'S'):

                 break;
             default:
                 goto skip_tag;
             }
         }
 

         metadatap = &p->metadata;

         switch (tag) {

         case MKTAG('I', 'H', 'D', 'R'):

             if ((ret = decode_ihdr_chunk(avctx, s, length)) < 0)

                 goto fail;
             break;

         case MKTAG('p', 'H', 'Y', 's'):

             if ((ret = decode_phys_chunk(avctx, s)) < 0)

                 goto fail;
             break;

         case MKTAG('f', 'c', 'T', 'L'):

             if (!CONFIG_APNG_DECODER || avctx->codec_id != AV_CODEC_ID_APNG)

                 goto skip_tag;
             if ((ret = decode_fctl_chunk(avctx, s, length)) < 0)
                 goto fail;
             decode_next_dat = 1;
             break;
         case MKTAG('f', 'd', 'A', 'T'):

             if (!CONFIG_APNG_DECODER || avctx->codec_id != AV_CODEC_ID_APNG)

                 goto skip_tag;

             if (!decode_next_dat) {
                 ret = AVERROR_INVALIDDATA;

                 goto fail;

             }

             bytestream2_get_be32(&s->gb);
             length -= 4;
             /* fallthrough */

         case MKTAG('I', 'D', 'A', 'T'):

             if (CONFIG_APNG_DECODER && avctx->codec_id == AV_CODEC_ID_APNG && !decode_next_dat)

                 goto skip_tag;

             if ((ret = decode_idat_chunk(avctx, s, length, p)) < 0)

                 goto fail;
             break;
         case MKTAG('P', 'L', 'T', 'E'):

             if (decode_plte_chunk(avctx, s, length) < 0)

                 goto skip_tag;

             break;

         case MKTAG('t', 'R', 'N', 'S'):

             if (decode_trns_chunk(avctx, s, length) < 0)

                 goto skip_tag;

             break;

         case MKTAG('t', 'E', 'X', 't'):

             if (decode_text_chunk(s, length, 0, metadatap) < 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, metadatap) < 0)

                 av_log(avctx, AV_LOG_WARNING, "Broken zTXt chunk\n");
             bytestream2_skip(&s->gb, length + 4);
             break;

         case MKTAG('s', 'T', 'E', 'R'): {

             int mode = bytestream2_get_byte(&s->gb);

             AVStereo3D *stereo3d = av_stereo3d_create_side_data(p);

             if (!stereo3d)

                 goto fail;

 
             if (mode == 0 || mode == 1) {

                 stereo3d->type  = AV_STEREO3D_SIDEBYSIDE;

                 stereo3d->flags = mode ? 0 : AV_STEREO3D_FLAG_INVERT;

             } else {

                  av_log(avctx, AV_LOG_WARNING,
                         "Unknown value in sTER chunk (%d)\n", mode);

             }

             bytestream2_skip(&s->gb, 4); /* crc */

             break;
         }

         case MKTAG('i', 'C', 'C', 'P'): {
             if (decode_iccp_chunk(s, length, p) < 0)
                 goto fail;
             break;
         }

         case MKTAG('c', 'H', 'R', 'M'): {
             AVMasteringDisplayMetadata *mdm = av_mastering_display_metadata_create_side_data(p);
             if (!mdm) {
                 ret = AVERROR(ENOMEM);
                 goto fail;
             }
 
             mdm->white_point[0] = av_make_q(bytestream2_get_be32(&s->gb), 100000);
             mdm->white_point[1] = av_make_q(bytestream2_get_be32(&s->gb), 100000);
 
             /* RGB Primaries */
             for (i = 0; i < 3; i++) {
                 mdm->display_primaries[i][0] = av_make_q(bytestream2_get_be32(&s->gb), 100000);
                 mdm->display_primaries[i][1] = av_make_q(bytestream2_get_be32(&s->gb), 100000);
             }
 
             mdm->has_primaries = 1;
             bytestream2_skip(&s->gb, 4); /* crc */
             break;
         }
         case MKTAG('g', 'A', 'M', 'A'): {
             AVBPrint bp;
             char *gamma_str;
             int num = bytestream2_get_be32(&s->gb);
 
             av_bprint_init(&bp, 0, -1);
             av_bprintf(&bp, "%i/%i", num, 100000);

             ret = av_bprint_finalize(&bp, &gamma_str);
             if (ret < 0)
                 return ret;

 
             av_dict_set(&p->metadata, "gamma", gamma_str, AV_DICT_DONT_STRDUP_VAL);
 
             bytestream2_skip(&s->gb, 4); /* crc */
             break;
         }

         case MKTAG('I', 'E', 'N', 'D'):

             if (!(s->pic_state & PNG_ALLIMAGE))

                 av_log(avctx, AV_LOG_ERROR, "IEND without all image\n");

             if (!(s->pic_state & (PNG_ALLIMAGE|PNG_IDAT))) {

                 ret = AVERROR_INVALIDDATA;

                 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 (avctx->codec_id == AV_CODEC_ID_PNG &&
         avctx->skip_frame == AVDISCARD_ALL) {
         return 0;
     }

     if (s->bits_per_pixel <= 4)
         handle_small_bpp(s, p);

     /* apply transparency if needed */
     if (s->has_trns && s->color_type != PNG_COLOR_TYPE_PALETTE) {
         size_t byte_depth = s->bit_depth > 8 ? 2 : 1;
         size_t raw_bpp = s->bpp - byte_depth;
         unsigned x, y;
 

         av_assert0(s->bit_depth > 1);
 

         for (y = 0; y < s->height; ++y) {
             uint8_t *row = &s->image_buf[s->image_linesize * y];
 
             /* since we're updating in-place, we have to go from right to left */
             for (x = s->width; x > 0; --x) {
                 uint8_t *pixel = &row[s->bpp * (x - 1)];
                 memmove(pixel, &row[raw_bpp * (x - 1)], raw_bpp);
 
                 if (!memcmp(pixel, s->transparent_color_be, raw_bpp)) {
                     memset(&pixel[raw_bpp], 0, byte_depth);
                 } else {
                     memset(&pixel[raw_bpp], 0xff, byte_depth);
                 }
             }
         }
     }
 

     /* handle P-frames only if a predecessor frame is available */

     if (s->last_picture.f->data[0]) {

         if (   !(avpkt->flags & AV_PKT_FLAG_KEY) && avctx->codec_tag != AV_RL32("MPNG")

             && s->last_picture.f->width == p->width
             && s->last_picture.f->height== p->height
             && s->last_picture.f->format== p->format

          ) {

             if (CONFIG_PNG_DECODER && avctx->codec_id != AV_CODEC_ID_APNG)

                 handle_p_frame_png(s, p);

             else if (CONFIG_APNG_DECODER &&
                      avctx->codec_id == AV_CODEC_ID_APNG &&
                      (ret = handle_p_frame_apng(avctx, s, p)) < 0)
                 goto fail;

         }
     }

     ff_thread_report_progress(&s->picture, INT_MAX, 0);

     ff_thread_report_progress(&s->previous_picture, INT_MAX, 0);

     return 0;
 
 fail:
     ff_thread_report_progress(&s->picture, INT_MAX, 0);

     ff_thread_report_progress(&s->previous_picture, INT_MAX, 0);

     return ret;

 }
 

 #if CONFIG_PNG_DECODER

 static int decode_frame_png(AVCodecContext *avctx,
                         void *data, int *got_frame,
                         AVPacket *avpkt)
 {
     PNGDecContext *const s = avctx->priv_data;
     const uint8_t *buf     = avpkt->data;
     int buf_size           = avpkt->size;
     AVFrame *p;
     int64_t sig;
     int ret;
 
     ff_thread_release_buffer(avctx, &s->last_picture);
     FFSWAP(ThreadFrame, s->picture, s->last_picture);
     p = s->picture.f;
 
     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, "Invalid PNG signature 0x%08"PRIX64".\n", sig);

         return AVERROR_INVALIDDATA;
     }
 

     s->y = s->has_trns = 0;
     s->hdr_state = 0;
     s->pic_state = 0;

 
     /* 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 error %d\n", ret);
         return AVERROR_EXTERNAL;
     }
 
     if ((ret = decode_frame_common(avctx, s, p, avpkt)) < 0)
         goto the_end;

     if (avctx->skip_frame == AVDISCARD_ALL) {
         *got_frame = 0;
         ret = bytestream2_tell(&s->gb);
         goto the_end;
     }
 

     if ((ret = av_frame_ref(data, s->picture.f)) < 0)

         goto the_end;

     *got_frame = 1;

     ret = bytestream2_tell(&s->gb);

 the_end:

     inflateEnd(&s->zstream);

     s->crow_buf = NULL;

     return ret;
 }

 #endif
 
 #if CONFIG_APNG_DECODER
 static int decode_frame_apng(AVCodecContext *avctx,
                         void *data, int *got_frame,
                         AVPacket *avpkt)
 {
     PNGDecContext *const s = avctx->priv_data;
     int ret;
     AVFrame *p;
 

     ff_thread_release_buffer(avctx, &s->last_picture);
     FFSWAP(ThreadFrame, s->picture, s->last_picture);

     p = s->picture.f;
 

     if (!(s->hdr_state & PNG_IHDR)) {

         if (!avctx->extradata_size)

             return AVERROR_INVALIDDATA;
 
         /* only init fields, there is no zlib use in extradata */
         s->zstream.zalloc = ff_png_zalloc;
         s->zstream.zfree  = ff_png_zfree;
 

         bytestream2_init(&s->gb, avctx->extradata, avctx->extradata_size);

         if ((ret = decode_frame_common(avctx, s, p, avpkt)) < 0)
             goto end;
     }
 
     /* reset state for a new frame */
     if ((ret = inflateInit(&s->zstream)) != Z_OK) {
         av_log(avctx, AV_LOG_ERROR, "inflateInit returned error %d\n", ret);
         ret = AVERROR_EXTERNAL;
         goto end;
     }
     s->y = 0;

     s->pic_state = 0;

     bytestream2_init(&s->gb, avpkt->data, avpkt->size);
     if ((ret = decode_frame_common(avctx, s, p, avpkt)) < 0)
         goto end;
 

     if (!(s->pic_state & PNG_ALLIMAGE))

         av_log(avctx, AV_LOG_WARNING, "Frame did not contain a complete image\n");

     if (!(s->pic_state & (PNG_ALLIMAGE|PNG_IDAT))) {

         ret = AVERROR_INVALIDDATA;
         goto end;
     }
     if ((ret = av_frame_ref(data, s->picture.f)) < 0)
         goto end;
 
     *got_frame = 1;
     ret = bytestream2_tell(&s->gb);
 
 end:
     inflateEnd(&s->zstream);
     return ret;
 }
 #endif

 #if HAVE_THREADS

 static int update_thread_context(AVCodecContext *dst, const AVCodecContext *src)
 {
     PNGDecContext *psrc = src->priv_data;
     PNGDecContext *pdst = dst->priv_data;

     int ret;

 
     if (dst == src)
         return 0;
 
     ff_thread_release_buffer(dst, &pdst->picture);

     if (psrc->picture.f->data[0] &&
         (ret = ff_thread_ref_frame(&pdst->picture, &psrc->picture)) < 0)
         return ret;
     if (CONFIG_APNG_DECODER && dst->codec_id == AV_CODEC_ID_APNG) {

         pdst->width             = psrc->width;
         pdst->height            = psrc->height;
         pdst->bit_depth         = psrc->bit_depth;
         pdst->color_type        = psrc->color_type;
         pdst->compression_type  = psrc->compression_type;
         pdst->interlace_type    = psrc->interlace_type;
         pdst->filter_type       = psrc->filter_type;

         pdst->cur_w = psrc->cur_w;
         pdst->cur_h = psrc->cur_h;
         pdst->x_offset = psrc->x_offset;
         pdst->y_offset = psrc->y_offset;

         pdst->has_trns = psrc->has_trns;

         memcpy(pdst->transparent_color_be, psrc->transparent_color_be, sizeof(pdst->transparent_color_be));

         pdst->dispose_op = psrc->dispose_op;
 

         memcpy(pdst->palette, psrc->palette, sizeof(pdst->palette));
 

         pdst->hdr_state |= psrc->hdr_state;

         ff_thread_release_buffer(dst, &pdst->last_picture);

         if (psrc->last_picture.f->data[0] &&
             (ret = ff_thread_ref_frame(&pdst->last_picture, &psrc->last_picture)) < 0)
             return ret;
 
         ff_thread_release_buffer(dst, &pdst->previous_picture);
         if (psrc->previous_picture.f->data[0] &&
             (ret = ff_thread_ref_frame(&pdst->previous_picture, &psrc->previous_picture)) < 0)
             return ret;

     }

 
     return 0;
 }

 #endif

 static av_cold int png_dec_init(AVCodecContext *avctx)
 {

     PNGDecContext *s = avctx->priv_data;
 

     avctx->color_range = AVCOL_RANGE_JPEG;
 

     s->avctx = avctx;

     s->previous_picture.f = av_frame_alloc();

     s->last_picture.f = av_frame_alloc();
     s->picture.f = av_frame_alloc();

     if (!s->previous_picture.f || !s->last_picture.f || !s->picture.f) {
         av_frame_free(&s->previous_picture.f);
         av_frame_free(&s->last_picture.f);
         av_frame_free(&s->picture.f);

         return AVERROR(ENOMEM);

     }

     if (!avctx->internal->is_copy) {
         avctx->internal->allocate_progress = 1;
         ff_pngdsp_init(&s->dsp);
     }

     return 0;
 }
 

 static av_cold int png_dec_end(AVCodecContext *avctx)
 {
     PNGDecContext *s = avctx->priv_data;
 

     ff_thread_release_buffer(avctx, &s->previous_picture);
     av_frame_free(&s->previous_picture.f);

     ff_thread_release_buffer(avctx, &s->last_picture);
     av_frame_free(&s->last_picture.f);
     ff_thread_release_buffer(avctx, &s->picture);
     av_frame_free(&s->picture.f);

     av_freep(&s->buffer);
     s->buffer_size = 0;
     av_freep(&s->last_row);
     s->last_row_size = 0;

     av_freep(&s->tmp_row);
     s->tmp_row_size = 0;

 
     return 0;
 }
 

 #if CONFIG_APNG_DECODER
 AVCodec ff_apng_decoder = {
     .name           = "apng",
     .long_name      = NULL_IF_CONFIG_SMALL("APNG (Animated Portable Network Graphics) image"),
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = AV_CODEC_ID_APNG,
     .priv_data_size = sizeof(PNGDecContext),
     .init           = png_dec_init,
     .close          = png_dec_end,
     .decode         = decode_frame_apng,
     .init_thread_copy = ONLY_IF_THREADS_ENABLED(png_dec_init),
     .update_thread_context = ONLY_IF_THREADS_ENABLED(update_thread_context),

     .capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_FRAME_THREADS /*| AV_CODEC_CAP_DRAW_HORIZ_BAND*/,

     .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,

 };
 #endif
 
 #if CONFIG_PNG_DECODER

 AVCodec ff_png_decoder = {

     .name           = "png",

     .long_name      = NULL_IF_CONFIG_SMALL("PNG (Portable Network Graphics) image"),

     .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_png,

     .init_thread_copy = ONLY_IF_THREADS_ENABLED(png_dec_init),
     .update_thread_context = ONLY_IF_THREADS_ENABLED(update_thread_context),

     .capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_FRAME_THREADS /*| AV_CODEC_CAP_DRAW_HORIZ_BAND*/,

     .caps_internal  = FF_CODEC_CAP_SKIP_FRAME_FILL_PARAM | FF_CODEC_CAP_INIT_THREADSAFE,

 };

 #endif