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/*
* GIF decoder
* Copyright (c) 2003 Fabrice Bellard
* Copyright (c) 2006 Baptiste Coudurier
*
* 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 "libavcore/imgutils.h"
#include "avcodec.h"
#include "bytestream.h"
#include "lzw.h"
#define GCE_DISPOSAL_NONE 0
#define GCE_DISPOSAL_INPLACE 1
#define GCE_DISPOSAL_BACKGROUND 2
#define GCE_DISPOSAL_RESTORE 3
typedef struct GifState {
AVFrame picture;
int screen_width;
int screen_height;
int bits_per_pixel;
int background_color_index;
int transparent_color_index;
int color_resolution;
uint32_t *image_palette;
/* after the frame is displayed, the disposal method is used */
int gce_disposal;
/* delay during which the frame is shown */
int gce_delay;
/* LZW compatible decoder */
const uint8_t *bytestream;
const uint8_t *bytestream_end;
LZWState *lzw;
/* aux buffers */
uint8_t global_palette[256 * 3];
uint8_t local_palette[256 * 3];
AVCodecContext* avctx;
} GifState;
static const uint8_t gif87a_sig[6] = "GIF87a";
static const uint8_t gif89a_sig[6] = "GIF89a";
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, n, i;
uint8_t *ptr, *spal, *palette, *ptr1;
left = bytestream_get_le16(&s->bytestream);
top = bytestream_get_le16(&s->bytestream);
width = bytestream_get_le16(&s->bytestream);
height = bytestream_get_le16(&s->bytestream);
flags = bytestream_get_byte(&s->bytestream);
is_interleaved = flags & 0x40;
has_local_palette = flags & 0x80;
bits_per_pixel = (flags & 0x07) + 1;
#ifdef DEBUG
dprintf(s->avctx, "gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
#endif
if (has_local_palette) {
bytestream_get_buffer(&s->bytestream, s->local_palette, 3 * (1 << bits_per_pixel));
palette = s->local_palette;
} else {
palette = s->global_palette;
bits_per_pixel = s->bits_per_pixel;
}
/* verify that all the image is inside the screen dimensions */
if (left + width > s->screen_width ||
top + height > s->screen_height)
return AVERROR(EINVAL);
/* build the palette */
n = (1 << bits_per_pixel);
spal = palette;
for(i = 0; i < n; i++) {
s->image_palette[i] = (0xff << 24) | AV_RB24(spal);
spal += 3;
}
for(; i < 256; i++)
s->image_palette[i] = (0xff << 24);
/* handle transparency */
if (s->transparent_color_index >= 0)
s->image_palette[s->transparent_color_index] = 0;
/* now get the image data */
code_size = bytestream_get_byte(&s->bytestream);
ff_lzw_decode_init(s->lzw, code_size, s->bytestream,
s->bytestream_end - s->bytestream, FF_LZW_GIF);
/* read all the image */
linesize = s->picture.linesize[0];
ptr1 = s->picture.data[0] + top * linesize + left;
ptr = ptr1;
pass = 0;
y1 = 0;
for (y = 0; y < height; y++) {
ff_lzw_decode(s->lzw, ptr, width);
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;
}
}
/* read the garbage data until end marker is found */
ff_lzw_decode_tail(s->lzw);
s->bytestream = ff_lzw_cur_ptr(s->lzw);
return 0;
}
static int gif_read_extension(GifState *s)
{
int ext_code, ext_len, i, gce_flags, gce_transparent_index;
/* extension */
ext_code = bytestream_get_byte(&s->bytestream);
ext_len = bytestream_get_byte(&s->bytestream);
#ifdef DEBUG
dprintf(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
#endif
switch(ext_code) {
case 0xf9:
if (ext_len != 4)
goto discard_ext;
s->transparent_color_index = -1;
gce_flags = bytestream_get_byte(&s->bytestream);
s->gce_delay = bytestream_get_le16(&s->bytestream);
gce_transparent_index = bytestream_get_byte(&s->bytestream);
if (gce_flags & 0x01)
s->transparent_color_index = gce_transparent_index;
else
s->transparent_color_index = -1;
s->gce_disposal = (gce_flags >> 2) & 0x7;
#ifdef DEBUG
dprintf(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
gce_flags, s->gce_delay,
s->transparent_color_index, s->gce_disposal);
#endif
ext_len = bytestream_get_byte(&s->bytestream);
break;
}
/* NOTE: many extension blocks can come after */
discard_ext:
while (ext_len != 0) {
for (i = 0; i < ext_len; i++)
bytestream_get_byte(&s->bytestream);
ext_len = bytestream_get_byte(&s->bytestream);
#ifdef DEBUG
dprintf(s->avctx, "gif: ext_len1=%d\n", ext_len);
#endif
}
return 0;
}
static int gif_read_header1(GifState *s)
{
uint8_t sig[6];
int v, n;
int has_global_palette;
if (s->bytestream_end < s->bytestream + 13)
return -1;
/* read gif signature */
bytestream_get_buffer(&s->bytestream, sig, 6);
if (memcmp(sig, gif87a_sig, 6) != 0 &&
memcmp(sig, gif89a_sig, 6) != 0)
return -1;
/* read screen header */
s->transparent_color_index = -1;
s->screen_width = bytestream_get_le16(&s->bytestream);
s->screen_height = bytestream_get_le16(&s->bytestream);
if( (unsigned)s->screen_width > 32767
|| (unsigned)s->screen_height > 32767){
av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
return -1;
}
v = bytestream_get_byte(&s->bytestream);
s->color_resolution = ((v & 0x70) >> 4) + 1;
has_global_palette = (v & 0x80);
s->bits_per_pixel = (v & 0x07) + 1;
s->background_color_index = bytestream_get_byte(&s->bytestream);
bytestream_get_byte(&s->bytestream); /* ignored */
#ifdef DEBUG
dprintf(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
s->screen_width, s->screen_height, s->bits_per_pixel,
has_global_palette);
#endif
if (has_global_palette) {
n = 1 << s->bits_per_pixel;
if (s->bytestream_end < s->bytestream + n * 3)
return -1;
bytestream_get_buffer(&s->bytestream, s->global_palette, n * 3);
}
return 0;
}
static int gif_parse_next_image(GifState *s)
{
while (s->bytestream < s->bytestream_end) {
int code = bytestream_get_byte(&s->bytestream);
#ifdef DEBUG
dprintf(s->avctx, "gif: code=%02x '%c'\n", code, code);
#endif
switch (code) {
case ',':
return gif_read_image(s);
case '!':
if (gif_read_extension(s) < 0)
return -1;
break;
case ';':
/* end of image */
default:
/* error or erroneous EOF */
return -1;
}
}
return -1;
}
static av_cold int gif_decode_init(AVCodecContext *avctx)
{
GifState *s = avctx->priv_data;
s->avctx = avctx;
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 *data_size, AVPacket *avpkt)
{
const uint8_t *buf = avpkt->data;
int buf_size = avpkt->size;
GifState *s = avctx->priv_data;
AVFrame *picture = data;
int ret;
s->bytestream = buf;
s->bytestream_end = buf + buf_size;
if (gif_read_header1(s) < 0)
return -1;
avctx->pix_fmt = PIX_FMT_PAL8;
if (av_image_check_size(s->screen_width, s->screen_height, 0, avctx))
return -1;
avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);
if (s->picture.data[0])
avctx->release_buffer(avctx, &s->picture);
if (avctx->get_buffer(avctx, &s->picture) < 0) {
av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
return -1;
}
s->image_palette = (uint32_t *)s->picture.data[1];
ret = gif_parse_next_image(s);
if (ret < 0)
return ret;
*picture = s->picture;
*data_size = sizeof(AVPicture);
return s->bytestream - buf;
}
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);
return 0;
}
AVCodec gif_decoder = {
"gif",
AVMEDIA_TYPE_VIDEO,
CODEC_ID_GIF,
sizeof(GifState),
gif_decode_init,
NULL,
gif_decode_close,
gif_decode_frame,
CODEC_CAP_DR1,
.long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
};
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