libavcodec/gifdec.c - third_party/ffmpeg - Git at Google

 /*
  * GIF decoder
  * Copyright (c) 2003 Fabrice Bellard
  * Copyright (c) 2006 Baptiste Coudurier
  * Copyright (c) 2012 Vitaliy E Sugrobov
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */

 //#define DEBUG

 #include "libavutil/imgutils.h"
 #include "libavutil/opt.h"
 #include "avcodec.h"
 #include "bytestream.h"
 #include "internal.h"
 #include "lzw.h"
 #include "gif.h"

 /* This value is intentionally set to "transparent white" color.
  * It is much better to have white background instead of black
  * when gif image converted to format which not support transparency.
  */
 #define GIF_TRANSPARENT_COLOR    0x00ffffff

 typedef struct GifState {
     const AVClass *class;
     AVFrame picture;
     int screen_width;
     int screen_height;
     int has_global_palette;
     int bits_per_pixel;
     uint32_t bg_color;
     int background_color_index;
     int transparent_color_index;
     int color_resolution;
     /* intermediate buffer for storing color indices
      * obtained from lzw-encoded data stream */
     uint8_t *idx_line;
     int idx_line_size;

     /* after the frame is displayed, the disposal method is used */
     int gce_prev_disposal;
     int gce_disposal;
     /* rectangle describing area that must be disposed */
     int gce_l, gce_t, gce_w, gce_h;
     /* depending on disposal method we store either part of the image
      * drawn on the canvas or background color that
      * should be used upon disposal */
     uint32_t * stored_img;
     int stored_img_size;
     int stored_bg_color;

     GetByteContext gb;
     /* LZW compatible decoder */
     LZWState *lzw;

     /* aux buffers */
     uint32_t global_palette[256];
     uint32_t local_palette[256];

     AVCodecContext *avctx;
     int keyframe;
     int keyframe_ok;
     int trans_color;    /**< color value that is used instead of transparent color */
 } GifState;

 static void gif_read_palette(GifState *s, uint32_t *pal, int nb)
 {
     int i;

     for (i = 0; i < nb; i++, pal++)
         *pal = (0xffu << 24) | bytestream2_get_be24u(&s->gb);
 }

 static void gif_fill(AVFrame *picture, uint32_t color)
 {
     uint32_t *p = (uint32_t *)picture->data[0];
     uint32_t *p_end = p + (picture->linesize[0] / sizeof(uint32_t)) * picture->height;

     for (; p < p_end; p++)
         *p = color;
 }

 static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)
 {
     const int linesize = picture->linesize[0] / sizeof(uint32_t);
     const uint32_t *py = (uint32_t *)picture->data[0] + t * linesize;
     const uint32_t *pr, *pb = py + h * linesize;
     uint32_t *px;

     for (; py < pb; py += linesize) {
         px = (uint32_t *)py + l;
         pr = px + w;

         for (; px < pr; px++)
             *px = color;
     }
 }

 static void gif_copy_img_rect(const uint32_t *src, uint32_t *dst,
                               int linesize, int l, int t, int w, int h)
 {
     const int y_start = t * linesize;
     const uint32_t *src_px, *src_pr,
                    *src_py = src + y_start,
                    *dst_py = dst + y_start;
     const uint32_t *src_pb = src_py + h * linesize;
     uint32_t *dst_px;

     for (; src_py < src_pb; src_py += linesize, dst_py += linesize) {
         src_px = src_py + l;
         dst_px = (uint32_t *)dst_py + l;
         src_pr = src_px + w;

         for (; src_px < src_pr; src_px++, dst_px++)
             *dst_px = *src_px;
     }
 }

 static int gif_read_image(GifState *s)
 {
     int left, top, width, height, bits_per_pixel, code_size, flags;
     int is_interleaved, has_local_palette, y, pass, y1, linesize, pal_size;
     uint32_t *ptr, *pal, *px, *pr, *ptr1;
     int ret;
     uint8_t *idx;

     /* At least 9 bytes of Image Descriptor. */
     if (bytestream2_get_bytes_left(&s->gb) < 9)
         return AVERROR_INVALIDDATA;

     left = bytestream2_get_le16u(&s->gb);
     top = bytestream2_get_le16u(&s->gb);
     width = bytestream2_get_le16u(&s->gb);
     height = bytestream2_get_le16u(&s->gb);
     flags = bytestream2_get_byteu(&s->gb);
     is_interleaved = flags & 0x40;
     has_local_palette = flags & 0x80;
     bits_per_pixel = (flags & 0x07) + 1;

     av_dlog(s->avctx, "image x=%d y=%d w=%d h=%d\n", left, top, width, height);

     if (has_local_palette) {
         pal_size = 1 << bits_per_pixel;

         if (bytestream2_get_bytes_left(&s->gb) < pal_size * 3)
             return AVERROR_INVALIDDATA;

         gif_read_palette(s, s->local_palette, pal_size);
         pal = s->local_palette;
     } else {
         if (!s->has_global_palette) {
             av_log(s->avctx, AV_LOG_ERROR, "picture doesn't have either global or local palette.\n");
             return AVERROR_INVALIDDATA;
         }

         pal = s->global_palette;
     }

     if (s->keyframe) {
         if (s->transparent_color_index == -1 && s->has_global_palette) {
             /* transparency wasn't set before the first frame, fill with background color */
             gif_fill(&s->picture, s->bg_color);
         } else {
             /* otherwise fill with transparent color.
              * this is necessary since by default picture filled with 0x80808080. */
             gif_fill(&s->picture, s->trans_color);
         }
     }

     /* verify that all the image is inside the screen dimensions */
     if (left + width > s->screen_width ||
         top + height > s->screen_height)
         return AVERROR_INVALIDDATA;

     /* process disposal method */
     if (s->gce_prev_disposal == GCE_DISPOSAL_BACKGROUND) {
         gif_fill_rect(&s->picture, s->stored_bg_color, s->gce_l, s->gce_t, s->gce_w, s->gce_h);
     } else if (s->gce_prev_disposal == GCE_DISPOSAL_RESTORE) {
         gif_copy_img_rect(s->stored_img, (uint32_t *)s->picture.data[0],
             s->picture.linesize[0] / sizeof(uint32_t), s->gce_l, s->gce_t, s->gce_w, s->gce_h);
     }

     s->gce_prev_disposal = s->gce_disposal;

     if (s->gce_disposal != GCE_DISPOSAL_NONE) {
         s->gce_l = left;  s->gce_t = top;
         s->gce_w = width; s->gce_h = height;

         if (s->gce_disposal == GCE_DISPOSAL_BACKGROUND) {
             if (s->transparent_color_index >= 0)
                 s->stored_bg_color = s->trans_color;
             else
                 s->stored_bg_color = s->bg_color;
         } else if (s->gce_disposal == GCE_DISPOSAL_RESTORE) {
             av_fast_malloc(&s->stored_img, &s->stored_img_size, s->picture.linesize[0] * s->picture.height);
             if (!s->stored_img)
                 return AVERROR(ENOMEM);

             gif_copy_img_rect((uint32_t *)s->picture.data[0], s->stored_img,
                 s->picture.linesize[0] / sizeof(uint32_t), left, top, width, height);
         }
     }

     /* Expect at least 2 bytes: 1 for lzw code size and 1 for block size. */
     if (bytestream2_get_bytes_left(&s->gb) < 2)
         return AVERROR_INVALIDDATA;

     /* now get the image data */
     code_size = bytestream2_get_byteu(&s->gb);
     if ((ret = ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
                                   bytestream2_get_bytes_left(&s->gb), FF_LZW_GIF)) < 0) {
         av_log(s->avctx, AV_LOG_ERROR, "LZW init failed\n");
         return ret;
     }

     /* read all the image */
     linesize = s->picture.linesize[0] / sizeof(uint32_t);
     ptr1 = (uint32_t *)s->picture.data[0] + top * linesize + left;
     ptr = ptr1;
     pass = 0;
     y1 = 0;
     for (y = 0; y < height; y++) {
         if (ff_lzw_decode(s->lzw, s->idx_line, width) == 0)
             goto decode_tail;

         pr = ptr + width;

         for (px = ptr, idx = s->idx_line; px < pr; px++, idx++) {
             if (*idx != s->transparent_color_index)
                 *px = pal[*idx];
         }

         if (is_interleaved) {
             switch(pass) {
             default:
             case 0:
             case 1:
                 y1 += 8;
                 ptr += linesize * 8;
                 if (y1 >= height) {
                     y1 = pass ? 2 : 4;
                     ptr = ptr1 + linesize * y1;
                     pass++;
                 }
                 break;
             case 2:
                 y1 += 4;
                 ptr += linesize * 4;
                 if (y1 >= height) {
                     y1 = 1;
                     ptr = ptr1 + linesize;
                     pass++;
                 }
                 break;
             case 3:
                 y1 += 2;
                 ptr += linesize * 2;
                 break;
             }
         } else {
             ptr += linesize;
         }
     }

  decode_tail:
     /* read the garbage data until end marker is found */
     ff_lzw_decode_tail(s->lzw);

     /* Graphic Control Extension's scope is single frame.
      * Remove its influence. */
     s->transparent_color_index = -1;
     s->gce_disposal = GCE_DISPOSAL_NONE;

     return 0;
 }

 static int gif_read_extension(GifState *s)
 {
     int ext_code, ext_len, gce_flags, gce_transparent_index;

     /* There must be at least 2 bytes:
      * 1 for extension label and 1 for extension length. */
     if (bytestream2_get_bytes_left(&s->gb) < 2)
         return AVERROR_INVALIDDATA;

     ext_code = bytestream2_get_byteu(&s->gb);
     ext_len = bytestream2_get_byteu(&s->gb);

     av_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);

     switch(ext_code) {
     case GIF_GCE_EXT_LABEL:
         if (ext_len != 4)
             goto discard_ext;

         /* We need at least 5 bytes more: 4 is for extension body
          * and 1 for next block size. */
         if (bytestream2_get_bytes_left(&s->gb) < 5)
             return AVERROR_INVALIDDATA;

         gce_flags = bytestream2_get_byteu(&s->gb);
         bytestream2_skipu(&s->gb, 2);    // delay during which the frame is shown
         gce_transparent_index = bytestream2_get_byteu(&s->gb);
         if (gce_flags & 0x01)
             s->transparent_color_index = gce_transparent_index;
         else
             s->transparent_color_index = -1;
         s->gce_disposal = (gce_flags >> 2) & 0x7;

         av_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",
                gce_flags,
                s->transparent_color_index, s->gce_disposal);

         if (s->gce_disposal > 3) {
             s->gce_disposal = GCE_DISPOSAL_NONE;
             av_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);
         }

         ext_len = bytestream2_get_byteu(&s->gb);
         break;
     }

     /* NOTE: many extension blocks can come after */
  discard_ext:
     while (ext_len != 0) {
         /* There must be at least ext_len bytes and 1 for next block size byte. */
         if (bytestream2_get_bytes_left(&s->gb) < ext_len + 1)
             return AVERROR_INVALIDDATA;

         bytestream2_skipu(&s->gb, ext_len);
         ext_len = bytestream2_get_byteu(&s->gb);

         av_dlog(s->avctx, "ext_len1=%d\n", ext_len);
     }
     return 0;
 }

 static int gif_read_header1(GifState *s)
 {
     uint8_t sig[6];
     int v, n;
     int background_color_index;

     if (bytestream2_get_bytes_left(&s->gb) < 13)
         return AVERROR_INVALIDDATA;

     /* read gif signature */
     bytestream2_get_bufferu(&s->gb, sig, 6);
     if (memcmp(sig, gif87a_sig, 6) != 0 &&
         memcmp(sig, gif89a_sig, 6) != 0)
         return AVERROR_INVALIDDATA;

     /* read screen header */
     s->transparent_color_index = -1;
     s->screen_width = bytestream2_get_le16u(&s->gb);
     s->screen_height = bytestream2_get_le16u(&s->gb);
     if(   (unsigned)s->screen_width  > 32767
        || (unsigned)s->screen_height > 32767){
         av_log(s->avctx, AV_LOG_ERROR, "picture size too large\n");
         return AVERROR_INVALIDDATA;
     }

     av_fast_malloc(&s->idx_line, &s->idx_line_size, s->screen_width);
     if (!s->idx_line)
         return AVERROR(ENOMEM);

     v = bytestream2_get_byteu(&s->gb);
     s->color_resolution = ((v & 0x70) >> 4) + 1;
     s->has_global_palette = (v & 0x80);
     s->bits_per_pixel = (v & 0x07) + 1;
     background_color_index = bytestream2_get_byteu(&s->gb);
     n = bytestream2_get_byteu(&s->gb);
     if (n) {
         s->avctx->sample_aspect_ratio.num = n + 15;
         s->avctx->sample_aspect_ratio.den = 64;
     }

     av_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
            s->screen_width, s->screen_height, s->bits_per_pixel,
            s->has_global_palette);

     if (s->has_global_palette) {
         s->background_color_index = background_color_index;
         n = 1 << s->bits_per_pixel;
         if (bytestream2_get_bytes_left(&s->gb) < n * 3)
             return AVERROR_INVALIDDATA;

         gif_read_palette(s, s->global_palette, n);
         s->bg_color = s->global_palette[s->background_color_index];
     } else
         s->background_color_index = -1;

     return 0;
 }

 static int gif_parse_next_image(GifState *s, int *got_picture)
 {
     int ret;
     *got_picture = 1;
     while (bytestream2_get_bytes_left(&s->gb)) {
         int code = bytestream2_get_byte(&s->gb);

         av_dlog(s->avctx, "code=%02x '%c'\n", code, code);

         switch (code) {
         case GIF_IMAGE_SEPARATOR:
             return gif_read_image(s);
         case GIF_EXTENSION_INTRODUCER:
             if ((ret = gif_read_extension(s)) < 0)
                 return ret;
             break;
         case GIF_TRAILER:
             /* end of image */
             *got_picture = 0;
             return 0;
         default:
             /* erroneous block label */
             return AVERROR_INVALIDDATA;
         }
     }
     return AVERROR_EOF;
 }

 static av_cold int gif_decode_init(AVCodecContext *avctx)
 {
     GifState *s = avctx->priv_data;

     s->avctx = avctx;

     avctx->pix_fmt = AV_PIX_FMT_RGB32;
     avcodec_get_frame_defaults(&s->picture);
     avctx->coded_frame= &s->picture;
     s->picture.data[0] = NULL;
     ff_lzw_decode_open(&s->lzw);
     return 0;
 }

 static int gif_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
 {
     GifState *s = avctx->priv_data;
     AVFrame *picture = data;
     int ret;

     bytestream2_init(&s->gb, avpkt->data, avpkt->size);

     s->picture.pts          = avpkt->pts;
     s->picture.pkt_pts      = avpkt->pts;
     s->picture.pkt_dts      = avpkt->dts;
     s->picture.pkt_duration = avpkt->duration;

     if (avpkt->size >= 6) {
         s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||
                       memcmp(avpkt->data, gif89a_sig, 6) == 0;
     } else {
         s->keyframe = 0;
     }

     if (s->keyframe) {
         s->keyframe_ok = 0;
         s->gce_prev_disposal = GCE_DISPOSAL_NONE;
         if ((ret = gif_read_header1(s)) < 0)
             return ret;

         if ((ret = av_image_check_size(s->screen_width, s->screen_height, 0, avctx)) < 0)
             return ret;
         avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);

         if (s->picture.data[0])
             avctx->release_buffer(avctx, &s->picture);

         if ((ret = ff_get_buffer(avctx, &s->picture)) < 0) {
             av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
             return ret;
         }

         s->picture.pict_type = AV_PICTURE_TYPE_I;
         s->picture.key_frame = 1;
         s->keyframe_ok = 1;
     } else {
         if (!s->keyframe_ok) {
             av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");
             return AVERROR_INVALIDDATA;
         }

         if ((ret = avctx->reget_buffer(avctx, &s->picture)) < 0) {
             av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
             return ret;
         }

         s->picture.pict_type = AV_PICTURE_TYPE_P;
         s->picture.key_frame = 0;
     }

     ret = gif_parse_next_image(s, got_frame);
     if (ret < 0)
         return ret;
     else if (*got_frame)
         *picture = s->picture;

     return avpkt->size;
 }

 static av_cold int gif_decode_close(AVCodecContext *avctx)
 {
     GifState *s = avctx->priv_data;

     ff_lzw_decode_close(&s->lzw);
     if(s->picture.data[0])
         avctx->release_buffer(avctx, &s->picture);

     av_freep(&s->idx_line);
     av_freep(&s->stored_img);

     return 0;
 }

 static const AVOption options[] = {
     { "trans_color", "color value (ARGB) that is used instead of transparent color",
       offsetof(GifState, trans_color), AV_OPT_TYPE_INT,
       {.i64 = GIF_TRANSPARENT_COLOR}, 0, 0xffffffff,
       AV_OPT_FLAG_DECODING_PARAM|AV_OPT_FLAG_VIDEO_PARAM },
     { NULL },
 };

 static const AVClass decoder_class = {
     .class_name = "gif decoder",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
     .category   = AV_CLASS_CATEGORY_DECODER,
 };

 AVCodec ff_gif_decoder = {
     .name           = "gif",
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = AV_CODEC_ID_GIF,
     .priv_data_size = sizeof(GifState),
     .init           = gif_decode_init,
     .close          = gif_decode_close,
     .decode         = gif_decode_frame,
     .capabilities   = CODEC_CAP_DR1,
     .long_name      = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
     .priv_class     = &decoder_class,
 };
	/*
	* GIF decoder
	* Copyright (c) 2003 Fabrice Bellard
	* Copyright (c) 2006 Baptiste Coudurier
	* Copyright (c) 2012 Vitaliy E Sugrobov
	*
	* This file is part of FFmpeg.
	*
	* FFmpeg is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* FFmpeg is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with FFmpeg; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	//#define DEBUG

	#include "libavutil/imgutils.h"
	#include "libavutil/opt.h"
	#include "avcodec.h"
	#include "bytestream.h"
	#include "internal.h"
	#include "lzw.h"
	#include "gif.h"

	/* This value is intentionally set to "transparent white" color.
	* It is much better to have white background instead of black
	* when gif image converted to format which not support transparency.
	*/
	#define GIF_TRANSPARENT_COLOR 0x00ffffff

	typedef struct GifState {
	const AVClass *class;
	AVFrame picture;
	int screen_width;
	int screen_height;
	int has_global_palette;
	int bits_per_pixel;
	uint32_t bg_color;
	int background_color_index;
	int transparent_color_index;
	int color_resolution;
	/* intermediate buffer for storing color indices
	* obtained from lzw-encoded data stream */
	uint8_t *idx_line;
	int idx_line_size;

	/* after the frame is displayed, the disposal method is used */
	int gce_prev_disposal;
	int gce_disposal;
	/* rectangle describing area that must be disposed */
	int gce_l, gce_t, gce_w, gce_h;
	/* depending on disposal method we store either part of the image
	* drawn on the canvas or background color that
	* should be used upon disposal */
	uint32_t * stored_img;
	int stored_img_size;
	int stored_bg_color;

	GetByteContext gb;
	/* LZW compatible decoder */
	LZWState *lzw;

	/* aux buffers */
	uint32_t global_palette[256];
	uint32_t local_palette[256];

	AVCodecContext *avctx;
	int keyframe;
	int keyframe_ok;
	int trans_color; /*< color value that is used instead of transparent color /
	} GifState;

	static void gif_read_palette(GifState s, uint32_t pal, int nb)
	{
	int i;

	for (i = 0; i < nb; i++, pal++)
	*pal = (0xffu << 24) \| bytestream2_get_be24u(&s->gb);
	}

	static void gif_fill(AVFrame *picture, uint32_t color)
	{
	uint32_t p = (uint32_t )picture->data[0];
	uint32_t p_end = p + (picture->linesize[0] / sizeof(uint32_t)) picture->height;

	for (; p < p_end; p++)
	*p = color;
	}

	static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)
	{
	const int linesize = picture->linesize[0] / sizeof(uint32_t);
	const uint32_t py = (uint32_t )picture->data[0] + t * linesize;
	const uint32_t pr, pb = py + h * linesize;
	uint32_t *px;

	for (; py < pb; py += linesize) {
	px = (uint32_t *)py + l;
	pr = px + w;

	for (; px < pr; px++)
	*px = color;
	}
	}

	static void gif_copy_img_rect(const uint32_t src, uint32_t dst,
	int linesize, int l, int t, int w, int h)
	{
	const int y_start = t * linesize;
	const uint32_t src_px, src_pr,
	*src_py = src + y_start,
	*dst_py = dst + y_start;
	const uint32_t src_pb = src_py + h linesize;
	uint32_t *dst_px;

	for (; src_py < src_pb; src_py += linesize, dst_py += linesize) {
	src_px = src_py + l;
	dst_px = (uint32_t *)dst_py + l;
	src_pr = src_px + w;

	for (; src_px < src_pr; src_px++, dst_px++)
	dst_px = src_px;
	}
	}

	static int gif_read_image(GifState *s)
	{
	int left, top, width, height, bits_per_pixel, code_size, flags;
	int is_interleaved, has_local_palette, y, pass, y1, linesize, pal_size;
	uint32_t ptr, pal, px, pr, *ptr1;
	int ret;
	uint8_t *idx;

	/* At least 9 bytes of Image Descriptor. */
	if (bytestream2_get_bytes_left(&s->gb) < 9)
	return AVERROR_INVALIDDATA;

	left = bytestream2_get_le16u(&s->gb);
	top = bytestream2_get_le16u(&s->gb);
	width = bytestream2_get_le16u(&s->gb);
	height = bytestream2_get_le16u(&s->gb);
	flags = bytestream2_get_byteu(&s->gb);
	is_interleaved = flags & 0x40;
	has_local_palette = flags & 0x80;
	bits_per_pixel = (flags & 0x07) + 1;

	av_dlog(s->avctx, "image x=%d y=%d w=%d h=%d\n", left, top, width, height);

	if (has_local_palette) {
	pal_size = 1 << bits_per_pixel;

	if (bytestream2_get_bytes_left(&s->gb) < pal_size * 3)
	return AVERROR_INVALIDDATA;

	gif_read_palette(s, s->local_palette, pal_size);
	pal = s->local_palette;
	} else {
	if (!s->has_global_palette) {
	av_log(s->avctx, AV_LOG_ERROR, "picture doesn't have either global or local palette.\n");
	return AVERROR_INVALIDDATA;
	}

	pal = s->global_palette;
	}

	if (s->keyframe) {
	if (s->transparent_color_index == -1 && s->has_global_palette) {
	/* transparency wasn't set before the first frame, fill with background color */
	gif_fill(&s->picture, s->bg_color);
	} else {
	/* otherwise fill with transparent color.
	* this is necessary since by default picture filled with 0x80808080. */
	gif_fill(&s->picture, s->trans_color);
	}
	}

	/* verify that all the image is inside the screen dimensions */
	if (left + width > s->screen_width \|\|
	top + height > s->screen_height)
	return AVERROR_INVALIDDATA;

	/* process disposal method */
	if (s->gce_prev_disposal == GCE_DISPOSAL_BACKGROUND) {
	gif_fill_rect(&s->picture, s->stored_bg_color, s->gce_l, s->gce_t, s->gce_w, s->gce_h);
	} else if (s->gce_prev_disposal == GCE_DISPOSAL_RESTORE) {
	gif_copy_img_rect(s->stored_img, (uint32_t *)s->picture.data[0],
	s->picture.linesize[0] / sizeof(uint32_t), s->gce_l, s->gce_t, s->gce_w, s->gce_h);
	}

	s->gce_prev_disposal = s->gce_disposal;

	if (s->gce_disposal != GCE_DISPOSAL_NONE) {
	s->gce_l = left; s->gce_t = top;
	s->gce_w = width; s->gce_h = height;

	if (s->gce_disposal == GCE_DISPOSAL_BACKGROUND) {
	if (s->transparent_color_index >= 0)
	s->stored_bg_color = s->trans_color;
	else
	s->stored_bg_color = s->bg_color;
	} else if (s->gce_disposal == GCE_DISPOSAL_RESTORE) {
	av_fast_malloc(&s->stored_img, &s->stored_img_size, s->picture.linesize[0] * s->picture.height);
	if (!s->stored_img)
	return AVERROR(ENOMEM);

	gif_copy_img_rect((uint32_t *)s->picture.data[0], s->stored_img,
	s->picture.linesize[0] / sizeof(uint32_t), left, top, width, height);
	}
	}

	/* Expect at least 2 bytes: 1 for lzw code size and 1 for block size. */
	if (bytestream2_get_bytes_left(&s->gb) < 2)
	return AVERROR_INVALIDDATA;

	/* now get the image data */
	code_size = bytestream2_get_byteu(&s->gb);
	if ((ret = ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
	bytestream2_get_bytes_left(&s->gb), FF_LZW_GIF)) < 0) {
	av_log(s->avctx, AV_LOG_ERROR, "LZW init failed\n");
	return ret;
	}

	/* read all the image */
	linesize = s->picture.linesize[0] / sizeof(uint32_t);
	ptr1 = (uint32_t )s->picture.data[0] + top linesize + left;
	ptr = ptr1;
	pass = 0;
	y1 = 0;
	for (y = 0; y < height; y++) {
	if (ff_lzw_decode(s->lzw, s->idx_line, width) == 0)
	goto decode_tail;

	pr = ptr + width;

	for (px = ptr, idx = s->idx_line; px < pr; px++, idx++) {
	if (*idx != s->transparent_color_index)
	px = pal[idx];
	}

	if (is_interleaved) {
	switch(pass) {
	default:
	case 0:
	case 1:
	y1 += 8;
	ptr += linesize * 8;
	if (y1 >= height) {
	y1 = pass ? 2 : 4;
	ptr = ptr1 + linesize * y1;
	pass++;
	}
	break;
	case 2:
	y1 += 4;
	ptr += linesize * 4;
	if (y1 >= height) {
	y1 = 1;
	ptr = ptr1 + linesize;
	pass++;
	}
	break;
	case 3:
	y1 += 2;
	ptr += linesize * 2;
	break;
	}
	} else {
	ptr += linesize;
	}
	}

	decode_tail:
	/* read the garbage data until end marker is found */
	ff_lzw_decode_tail(s->lzw);

	/* Graphic Control Extension's scope is single frame.
	* Remove its influence. */
	s->transparent_color_index = -1;
	s->gce_disposal = GCE_DISPOSAL_NONE;

	return 0;
	}

	static int gif_read_extension(GifState *s)
	{
	int ext_code, ext_len, gce_flags, gce_transparent_index;

	/* There must be at least 2 bytes:
	* 1 for extension label and 1 for extension length. */
	if (bytestream2_get_bytes_left(&s->gb) < 2)
	return AVERROR_INVALIDDATA;

	ext_code = bytestream2_get_byteu(&s->gb);
	ext_len = bytestream2_get_byteu(&s->gb);

	av_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);

	switch(ext_code) {
	case GIF_GCE_EXT_LABEL:
	if (ext_len != 4)
	goto discard_ext;

	/* We need at least 5 bytes more: 4 is for extension body
	* and 1 for next block size. */
	if (bytestream2_get_bytes_left(&s->gb) < 5)
	return AVERROR_INVALIDDATA;

	gce_flags = bytestream2_get_byteu(&s->gb);
	bytestream2_skipu(&s->gb, 2); // delay during which the frame is shown
	gce_transparent_index = bytestream2_get_byteu(&s->gb);
	if (gce_flags & 0x01)
	s->transparent_color_index = gce_transparent_index;
	else
	s->transparent_color_index = -1;
	s->gce_disposal = (gce_flags >> 2) & 0x7;

	av_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",
	gce_flags,
	s->transparent_color_index, s->gce_disposal);

	if (s->gce_disposal > 3) {
	s->gce_disposal = GCE_DISPOSAL_NONE;
	av_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);
	}

	ext_len = bytestream2_get_byteu(&s->gb);
	break;
	}

	/* NOTE: many extension blocks can come after */
	discard_ext:
	while (ext_len != 0) {
	/* There must be at least ext_len bytes and 1 for next block size byte. */
	if (bytestream2_get_bytes_left(&s->gb) < ext_len + 1)
	return AVERROR_INVALIDDATA;

	bytestream2_skipu(&s->gb, ext_len);
	ext_len = bytestream2_get_byteu(&s->gb);

	av_dlog(s->avctx, "ext_len1=%d\n", ext_len);
	}
	return 0;
	}

	static int gif_read_header1(GifState *s)
	{
	uint8_t sig[6];
	int v, n;
	int background_color_index;

	if (bytestream2_get_bytes_left(&s->gb) < 13)
	return AVERROR_INVALIDDATA;

	/* read gif signature */
	bytestream2_get_bufferu(&s->gb, sig, 6);
	if (memcmp(sig, gif87a_sig, 6) != 0 &&
	memcmp(sig, gif89a_sig, 6) != 0)
	return AVERROR_INVALIDDATA;

	/* read screen header */
	s->transparent_color_index = -1;
	s->screen_width = bytestream2_get_le16u(&s->gb);
	s->screen_height = bytestream2_get_le16u(&s->gb);
	if( (unsigned)s->screen_width > 32767
	\|\| (unsigned)s->screen_height > 32767){
	av_log(s->avctx, AV_LOG_ERROR, "picture size too large\n");
	return AVERROR_INVALIDDATA;
	}

	av_fast_malloc(&s->idx_line, &s->idx_line_size, s->screen_width);
	if (!s->idx_line)
	return AVERROR(ENOMEM);

	v = bytestream2_get_byteu(&s->gb);
	s->color_resolution = ((v & 0x70) >> 4) + 1;
	s->has_global_palette = (v & 0x80);
	s->bits_per_pixel = (v & 0x07) + 1;
	background_color_index = bytestream2_get_byteu(&s->gb);
	n = bytestream2_get_byteu(&s->gb);
	if (n) {
	s->avctx->sample_aspect_ratio.num = n + 15;
	s->avctx->sample_aspect_ratio.den = 64;
	}

	av_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
	s->screen_width, s->screen_height, s->bits_per_pixel,
	s->has_global_palette);

	if (s->has_global_palette) {
	s->background_color_index = background_color_index;
	n = 1 << s->bits_per_pixel;
	if (bytestream2_get_bytes_left(&s->gb) < n * 3)
	return AVERROR_INVALIDDATA;

	gif_read_palette(s, s->global_palette, n);
	s->bg_color = s->global_palette[s->background_color_index];
	} else
	s->background_color_index = -1;

	return 0;
	}

	static int gif_parse_next_image(GifState s, int got_picture)
	{
	int ret;
	*got_picture = 1;
	while (bytestream2_get_bytes_left(&s->gb)) {
	int code = bytestream2_get_byte(&s->gb);

	av_dlog(s->avctx, "code=%02x '%c'\n", code, code);

	switch (code) {
	case GIF_IMAGE_SEPARATOR:
	return gif_read_image(s);
	case GIF_EXTENSION_INTRODUCER:
	if ((ret = gif_read_extension(s)) < 0)
	return ret;
	break;
	case GIF_TRAILER:
	/* end of image */
	*got_picture = 0;
	return 0;
	default:
	/* erroneous block label */
	return AVERROR_INVALIDDATA;
	}
	}
	return AVERROR_EOF;
	}

	static av_cold int gif_decode_init(AVCodecContext *avctx)
	{
	GifState *s = avctx->priv_data;

	s->avctx = avctx;

	avctx->pix_fmt = AV_PIX_FMT_RGB32;
	avcodec_get_frame_defaults(&s->picture);
	avctx->coded_frame= &s->picture;
	s->picture.data[0] = NULL;
	ff_lzw_decode_open(&s->lzw);
	return 0;
	}

	static int gif_decode_frame(AVCodecContext avctx, void data, int got_frame, AVPacket avpkt)
	{
	GifState *s = avctx->priv_data;
	AVFrame *picture = data;
	int ret;

	bytestream2_init(&s->gb, avpkt->data, avpkt->size);

	s->picture.pts = avpkt->pts;
	s->picture.pkt_pts = avpkt->pts;
	s->picture.pkt_dts = avpkt->dts;
	s->picture.pkt_duration = avpkt->duration;

	if (avpkt->size >= 6) {
	s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 \|\|
	memcmp(avpkt->data, gif89a_sig, 6) == 0;
	} else {
	s->keyframe = 0;
	}

	if (s->keyframe) {
	s->keyframe_ok = 0;
	s->gce_prev_disposal = GCE_DISPOSAL_NONE;
	if ((ret = gif_read_header1(s)) < 0)
	return ret;

	if ((ret = av_image_check_size(s->screen_width, s->screen_height, 0, avctx)) < 0)
	return ret;
	avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);

	if (s->picture.data[0])
	avctx->release_buffer(avctx, &s->picture);

	if ((ret = ff_get_buffer(avctx, &s->picture)) < 0) {
	av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
	return ret;
	}

	s->picture.pict_type = AV_PICTURE_TYPE_I;
	s->picture.key_frame = 1;
	s->keyframe_ok = 1;
	} else {
	if (!s->keyframe_ok) {
	av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");
	return AVERROR_INVALIDDATA;
	}

	if ((ret = avctx->reget_buffer(avctx, &s->picture)) < 0) {
	av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
	return ret;
	}

	s->picture.pict_type = AV_PICTURE_TYPE_P;
	s->picture.key_frame = 0;
	}

	ret = gif_parse_next_image(s, got_frame);
	if (ret < 0)
	return ret;
	else if (*got_frame)
	*picture = s->picture;

	return avpkt->size;
	}

	static av_cold int gif_decode_close(AVCodecContext *avctx)
	{
	GifState *s = avctx->priv_data;

	ff_lzw_decode_close(&s->lzw);
	if(s->picture.data[0])
	avctx->release_buffer(avctx, &s->picture);

	av_freep(&s->idx_line);
	av_freep(&s->stored_img);

	return 0;
	}

	static const AVOption options[] = {
	{ "trans_color", "color value (ARGB) that is used instead of transparent color",
	offsetof(GifState, trans_color), AV_OPT_TYPE_INT,
	{.i64 = GIF_TRANSPARENT_COLOR}, 0, 0xffffffff,
	AV_OPT_FLAG_DECODING_PARAM\|AV_OPT_FLAG_VIDEO_PARAM },
	{ NULL },
	};

	static const AVClass decoder_class = {
	.class_name = "gif decoder",
	.item_name = av_default_item_name,
	.option = options,
	.version = LIBAVUTIL_VERSION_INT,
	.category = AV_CLASS_CATEGORY_DECODER,
	};

	AVCodec ff_gif_decoder = {
	.name = "gif",
	.type = AVMEDIA_TYPE_VIDEO,
	.id = AV_CODEC_ID_GIF,
	.priv_data_size = sizeof(GifState),
	.init = gif_decode_init,
	.close = gif_decode_close,
	.decode = gif_decode_frame,
	.capabilities = CODEC_CAP_DR1,
	.long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
	.priv_class = &decoder_class,
	};