FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/gifdec.c
Date: 2025-07-28 20:30:09
Exec Total Coverage
Lines: 201 271 74.2%
Functions: 11 11 100.0%
Branches: 92 141 65.2%
Line Branch Exec Source
1 /*
2 * GIF decoder
3 * Copyright (c) 2003 Fabrice Bellard
4 * Copyright (c) 2006 Baptiste Coudurier
5 * Copyright (c) 2012 Vitaliy E Sugrobov
6 *
7 * This file is part of FFmpeg.
8 *
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24 #include "libavutil/mem.h"
25 #include "libavutil/opt.h"
26 #include "avcodec.h"
27 #include "bytestream.h"
28 #include "codec_internal.h"
29 #include "decode.h"
30 #include "lzw.h"
31 #include "gif.h"
32
33 /* This value is intentionally set to "transparent white" color.
34 * It is much better to have white background instead of black
35 * when gif image converted to format which not support transparency.
36 */
37 #define GIF_TRANSPARENT_COLOR 0x00ffffff
38
39 typedef struct GifState {
40 const AVClass *class;
41 AVFrame *frame;
42 int screen_width;
43 int screen_height;
44 int has_global_palette;
45 int bits_per_pixel;
46 uint32_t bg_color;
47 int background_color_index;
48 int transparent_color_index;
49 int color_resolution;
50 /* intermediate buffer for storing color indices
51 * obtained from lzw-encoded data stream */
52 uint8_t *idx_line;
53 int idx_line_size;
54
55 /* after the frame is displayed, the disposal method is used */
56 int gce_prev_disposal;
57 int gce_disposal;
58 /* rectangle describing area that must be disposed */
59 int gce_l, gce_t, gce_w, gce_h;
60 /* depending on disposal method we store either part of the image
61 * drawn on the canvas or background color that
62 * should be used upon disposal */
63 uint8_t *stored_img;
64 int stored_img_size;
65 int stored_bg_color;
66
67 GetByteContext gb;
68 LZWState *lzw;
69
70 /* aux buffers */
71 uint32_t global_palette[256];
72 uint32_t local_palette[256];
73
74 AVCodecContext *avctx;
75 int keyframe;
76 int keyframe_ok;
77 int trans_color; /**< color value that is used instead of transparent color */
78 } GifState;
79
80 1219 static void gif_read_palette(GifState *s, uint32_t *pal, int nb)
81 {
82 int i;
83
84
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 300547 for (i = 0; i < nb; i++, pal++)
85 299328 *pal = (0xffu << 24) | bytestream2_get_be24u(&s->gb);
86 1219 }
87
88 13 static void gif_fill(AVFrame *picture, uint32_t color)
89 {
90 13 const ptrdiff_t linesize = picture->linesize[0];
91 13 uint8_t *py = picture->data[0];
92 13 const int w = picture->width;
93 13 const int h = picture->height;
94
95
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 2493 for (int y = 0; y < h; y++) {
96 2480 uint32_t *px = (uint32_t *)py;
97
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 717373 for (int x = 0; x < w; x++)
98 714893 px[x] = color;
99 2480 py += linesize;
100 }
101 13 }
102
103 6 static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)
104 {
105 6 const ptrdiff_t linesize = picture->linesize[0];
106 6 uint8_t *py = picture->data[0] + t * linesize;
107
108
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 222 for (int y = 0; y < h; y++) {
109 216 uint32_t *px = ((uint32_t *)py) + l;
110
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 15768 for (int x = 0; x < w; x++)
111 15552 px[x] = color;
112 216 py += linesize;
113 }
114 6 }
115
116 3 static void gif_copy_img_rect(const uint8_t *src, uint8_t *dst,
117 ptrdiff_t src_linesize,
118 ptrdiff_t dst_linesize,
119 int l, int t, int w, int h)
120 {
121 3 const uint8_t *src_py = src;
122 3 uint8_t *dst_py = dst;
123
124 3 src_py += t * src_linesize;
125 3 dst_py += t * dst_linesize;
126
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 183 for (int y = 0; y < h; y++) {
127 180 memcpy(dst_py + l * 4, src_py + l * 4, w * 4);
128 180 src_py += src_linesize;
129 180 dst_py += dst_linesize;
130 }
131 3 }
132
133 1294 static int gif_read_image(GifState *s, AVFrame *frame)
134 {
135 int left, top, width, height, bits_per_pixel, code_size, flags, pw;
136 int is_interleaved, has_local_palette, y, pass, y1, pal_size, lzwed_len;
137 uint32_t *ptr, *pal, *px, *pr, *ptr1;
138 ptrdiff_t linesize;
139 int ret;
140 uint8_t *idx;
141
142 /* At least 9 bytes of Image Descriptor. */
143
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 1294 if (bytestream2_get_bytes_left(&s->gb) < 9)
144 ✗ return AVERROR_INVALIDDATA;
145
146 1294 left = bytestream2_get_le16u(&s->gb);
147 1294 top = bytestream2_get_le16u(&s->gb);
148 1294 width = bytestream2_get_le16u(&s->gb);
149 1294 height = bytestream2_get_le16u(&s->gb);
150 1294 flags = bytestream2_get_byteu(&s->gb);
151 1294 is_interleaved = flags & 0x40;
152 1294 has_local_palette = flags & 0x80;
153 1294 bits_per_pixel = (flags & 0x07) + 1;
154
155 ff_dlog(s->avctx, "image x=%d y=%d w=%d h=%d\n", left, top, width, height);
156
157
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 1294 if (has_local_palette) {
158 1213 pal_size = 1 << bits_per_pixel;
159
160
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 1213 if (bytestream2_get_bytes_left(&s->gb) < pal_size * 3)
161 ✗ return AVERROR_INVALIDDATA;
162
163 1213 gif_read_palette(s, s->local_palette, pal_size);
164 1213 pal = s->local_palette;
165 } else {
166
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 81 if (!s->has_global_palette) {
167 ✗ av_log(s->avctx, AV_LOG_ERROR, "picture doesn't have either global or local palette.\n");
168 ✗ return AVERROR_INVALIDDATA;
169 }
170
171 81 pal = s->global_palette;
172 }
173
174
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 1294 if (s->keyframe) {
175
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 13 if (s->transparent_color_index == -1 && s->has_global_palette) {
176 /* transparency wasn't set before the first frame, fill with background color */
177 5 gif_fill(frame, s->bg_color);
178 } else {
179 /* otherwise fill with transparent color.
180 * this is necessary since by default picture filled with 0x80808080. */
181 8 gif_fill(frame, s->trans_color);
182 }
183 }
184
185 /* verify that all the image is inside the screen dimensions */
186
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 1294 if (!width || width > s->screen_width) {
187 ✗ av_log(s->avctx, AV_LOG_WARNING, "Invalid image width: %d, truncating.\n", width);
188 ✗ width = s->screen_width;
189 }
190
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 1294 if (left >= s->screen_width) {
191 ✗ av_log(s->avctx, AV_LOG_ERROR, "Invalid left position: %d.\n", left);
192 ✗ return AVERROR_INVALIDDATA;
193 }
194
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 1294 if (!height || height > s->screen_height) {
195 ✗ av_log(s->avctx, AV_LOG_WARNING, "Invalid image height: %d, truncating.\n", height);
196 ✗ height = s->screen_height;
197 }
198
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 1294 if (top >= s->screen_height) {
199 ✗ av_log(s->avctx, AV_LOG_ERROR, "Invalid top position: %d.\n", top);
200 ✗ return AVERROR_INVALIDDATA;
201 }
202
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 1294 if (left + width > s->screen_width) {
203 /* width must be kept around to avoid lzw vs line desync */
204 ✗ pw = s->screen_width - left;
205 ✗ av_log(s->avctx, AV_LOG_WARNING, "Image too wide by %d, truncating.\n",
206 ✗ left + width - s->screen_width);
207 } else {
208 1294 pw = width;
209 }
210
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 1294 if (top + height > s->screen_height) {
211 /* we don't care about the extra invisible lines */
212 ✗ av_log(s->avctx, AV_LOG_WARNING, "Image too high by %d, truncating.\n",
213 ✗ top + height - s->screen_height);
214 ✗ height = s->screen_height - top;
215 }
216
217 /* process disposal method */
218
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 1294 if (s->gce_prev_disposal == GCE_DISPOSAL_BACKGROUND) {
219 6 gif_fill_rect(frame, s->stored_bg_color, s->gce_l, s->gce_t, s->gce_w, s->gce_h);
220
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 1288 } else if (s->gce_prev_disposal == GCE_DISPOSAL_RESTORE) {
221 1 gif_copy_img_rect(s->stored_img, frame->data[0],
222 1 FFABS(frame->linesize[0]), frame->linesize[0], s->gce_l, s->gce_t, s->gce_w, s->gce_h);
223 }
224
225 1294 s->gce_prev_disposal = s->gce_disposal;
226
227
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 1294 if (s->gce_disposal != GCE_DISPOSAL_NONE) {
228 1293 s->gce_l = left; s->gce_t = top;
229 1293 s->gce_w = pw; s->gce_h = height;
230
231
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 1293 if (s->gce_disposal == GCE_DISPOSAL_BACKGROUND) {
232
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 8 if (s->transparent_color_index >= 0)
233 8 s->stored_bg_color = s->trans_color;
234 else
235 ✗ s->stored_bg_color = s->bg_color;
236
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 1285 } else if (s->gce_disposal == GCE_DISPOSAL_RESTORE) {
237 2 av_fast_malloc(&s->stored_img, &s->stored_img_size, FFABS(frame->linesize[0]) * frame->height);
238
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 2 if (!s->stored_img)
239 ✗ return AVERROR(ENOMEM);
240
241 2 gif_copy_img_rect(frame->data[0], s->stored_img,
242 2 frame->linesize[0], FFABS(frame->linesize[0]), left, top, pw, height);
243 }
244 }
245
246 /* Expect at least 2 bytes: 1 for lzw code size and 1 for block size. */
247
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 1294 if (bytestream2_get_bytes_left(&s->gb) < 2)
248 ✗ return AVERROR_INVALIDDATA;
249
250 /* now get the image data */
251 1294 code_size = bytestream2_get_byteu(&s->gb);
252
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 1294 if ((ret = ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
253 1294 bytestream2_get_bytes_left(&s->gb), FF_LZW_GIF)) < 0) {
254 ✗ av_log(s->avctx, AV_LOG_ERROR, "LZW init failed\n");
255 ✗ return ret;
256 }
257
258 /* read all the image */
259 1294 linesize = frame->linesize[0];
260 1294 ptr1 = (uint32_t *)(frame->data[0] + top * linesize) + left;
261 1294 ptr = ptr1;
262 1294 pass = 0;
263 1294 y1 = 0;
264
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 39267 for (y = 0; y < height; y++) {
265 37973 int count = ff_lzw_decode(s->lzw, s->idx_line, width);
266
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 37973 if (count != width) {
267 ✗ if (count)
268 ✗ av_log(s->avctx, AV_LOG_ERROR, "LZW decode failed\n");
269 ✗ goto decode_tail;
270 }
271
272 37973 pr = ptr + pw;
273
274
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 5366572 for (px = ptr, idx = s->idx_line; px < pr; px++, idx++) {
275
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 5328599 if (*idx != s->transparent_color_index)
276 3988325 *px = pal[*idx];
277 }
278
279
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 37973 if (is_interleaved) {
280 ✗ switch(pass) {
281 ✗ default:
282 case 0:
283 case 1:
284 ✗ y1 += 8;
285 ✗ ptr += linesize * 2;
286 ✗ break;
287 ✗ case 2:
288 ✗ y1 += 4;
289 ✗ ptr += linesize * 1;
290 ✗ break;
291 ✗ case 3:
292 ✗ y1 += 2;
293 ✗ ptr += linesize / 2;
294 ✗ break;
295 }
296 ✗ while (y1 >= height) {
297 ✗ y1 = 4 >> pass;
298 ✗ ptr = ptr1 + linesize / 4 * y1;
299 ✗ pass++;
300 }
301 } else {
302 37973 ptr += linesize / 4;
303 }
304 }
305
306 1294 decode_tail:
307 /* read the garbage data until end marker is found */
308 1294 lzwed_len = ff_lzw_decode_tail(s->lzw);
309 1294 bytestream2_skipu(&s->gb, lzwed_len);
310
311 /* Graphic Control Extension's scope is single frame.
312 * Remove its influence. */
313 1294 s->transparent_color_index = -1;
314 1294 s->gce_disposal = GCE_DISPOSAL_NONE;
315
316 1294 return 0;
317 }
318
319 1303 static int gif_read_extension(GifState *s)
320 {
321 int ext_code, ext_len, gce_flags, gce_transparent_index;
322
323 /* There must be at least 2 bytes:
324 * 1 for extension label and 1 for extension length. */
325
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 1303 if (bytestream2_get_bytes_left(&s->gb) < 2)
326 ✗ return AVERROR_INVALIDDATA;
327
328 1303 ext_code = bytestream2_get_byteu(&s->gb);
329 1303 ext_len = bytestream2_get_byteu(&s->gb);
330
331 ff_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);
332
333
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 1303 switch(ext_code) {
334 1294 case GIF_GCE_EXT_LABEL:
335
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 1294 if (ext_len != 4)
336 ✗ goto discard_ext;
337
338 /* We need at least 5 bytes more: 4 is for extension body
339 * and 1 for next block size. */
340
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 1294 if (bytestream2_get_bytes_left(&s->gb) < 5)
341 ✗ return AVERROR_INVALIDDATA;
342
343 1294 gce_flags = bytestream2_get_byteu(&s->gb);
344 1294 bytestream2_skipu(&s->gb, 2); // delay during which the frame is shown
345 1294 gce_transparent_index = bytestream2_get_byteu(&s->gb);
346
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 1294 if (gce_flags & 0x01)
347 46 s->transparent_color_index = gce_transparent_index;
348 else
349 1248 s->transparent_color_index = -1;
350 1294 s->gce_disposal = (gce_flags >> 2) & 0x7;
351
352 ff_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",
353 gce_flags,
354 s->transparent_color_index, s->gce_disposal);
355
356
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 1294 if (s->gce_disposal > 3) {
357 ✗ s->gce_disposal = GCE_DISPOSAL_NONE;
358 ff_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);
359 }
360
361 1294 ext_len = bytestream2_get_byteu(&s->gb);
362 1294 break;
363 }
364
365 /* NOTE: many extension blocks can come after */
366 1303 discard_ext:
367
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 1330 while (ext_len) {
368 /* There must be at least ext_len bytes and 1 for next block size byte. */
369
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 27 if (bytestream2_get_bytes_left(&s->gb) < ext_len + 1)
370 ✗ return AVERROR_INVALIDDATA;
371
372 27 bytestream2_skipu(&s->gb, ext_len);
373 27 ext_len = bytestream2_get_byteu(&s->gb);
374
375 ff_dlog(s->avctx, "ext_len1=%d\n", ext_len);
376 }
377 1303 return 0;
378 }
379
380 13 static int gif_read_header1(GifState *s)
381 {
382 uint8_t sig[6];
383 int v, n;
384 int background_color_index;
385
386
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 13 if (bytestream2_get_bytes_left(&s->gb) < 13)
387 ✗ return AVERROR_INVALIDDATA;
388
389 /* read gif signature */
390 13 bytestream2_get_bufferu(&s->gb, sig, 6);
391
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 13 if (memcmp(sig, gif87a_sig, 6) &&
392
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 13 memcmp(sig, gif89a_sig, 6))
393 ✗ return AVERROR_INVALIDDATA;
394
395 /* read screen header */
396 13 s->transparent_color_index = -1;
397 13 s->screen_width = bytestream2_get_le16u(&s->gb);
398 13 s->screen_height = bytestream2_get_le16u(&s->gb);
399
400 13 v = bytestream2_get_byteu(&s->gb);
401 13 s->color_resolution = ((v & 0x70) >> 4) + 1;
402 13 s->has_global_palette = (v & 0x80);
403 13 s->bits_per_pixel = (v & 0x07) + 1;
404 13 background_color_index = bytestream2_get_byteu(&s->gb);
405 13 n = bytestream2_get_byteu(&s->gb);
406
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 13 if (n) {
407 ✗ s->avctx->sample_aspect_ratio.num = n + 15;
408 ✗ s->avctx->sample_aspect_ratio.den = 64;
409 }
410
411 ff_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
412 s->screen_width, s->screen_height, s->bits_per_pixel,
413 s->has_global_palette);
414
415
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 13 if (s->has_global_palette) {
416 6 s->background_color_index = background_color_index;
417 6 n = 1 << s->bits_per_pixel;
418
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 6 if (bytestream2_get_bytes_left(&s->gb) < n * 3)
419 ✗ return AVERROR_INVALIDDATA;
420
421 6 gif_read_palette(s, s->global_palette, n);
422 6 s->bg_color = s->global_palette[s->background_color_index];
423 } else
424 7 s->background_color_index = -1;
425
426 13 return 0;
427 }
428
429 1294 static int gif_parse_next_image(GifState *s, AVFrame *frame)
430 {
431
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 2597 while (bytestream2_get_bytes_left(&s->gb) > 0) {
432 2597 int code = bytestream2_get_byte(&s->gb);
433 int ret;
434
435 2597 av_log(s->avctx, AV_LOG_DEBUG, "code=%02x '%c'\n", code, code);
436
437
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 2597 switch (code) {
438 1294 case GIF_IMAGE_SEPARATOR:
439 1294 return gif_read_image(s, frame);
440 1303 case GIF_EXTENSION_INTRODUCER:
441
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 1303 if ((ret = gif_read_extension(s)) < 0)
442 ✗ return ret;
443 1303 break;
444 ✗ case GIF_TRAILER:
445 /* end of image */
446 ✗ return AVERROR_EOF;
447 ✗ default:
448 /* erroneous block label */
449 ✗ return AVERROR_INVALIDDATA;
450 }
451 }
452 ✗ return AVERROR_EOF;
453 }
454
455 28 static av_cold int gif_decode_init(AVCodecContext *avctx)
456 {
457 28 GifState *s = avctx->priv_data;
458
459 28 s->avctx = avctx;
460
461 28 avctx->pix_fmt = AV_PIX_FMT_RGB32;
462 28 s->frame = av_frame_alloc();
463
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 28 if (!s->frame)
464 ✗ return AVERROR(ENOMEM);
465 28 ff_lzw_decode_open(&s->lzw);
466
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 28 if (!s->lzw)
467 ✗ return AVERROR(ENOMEM);
468 28 return 0;
469 }
470
471 1294 static int gif_decode_frame(AVCodecContext *avctx, AVFrame *rframe,
472 int *got_frame, AVPacket *avpkt)
473 {
474 1294 GifState *s = avctx->priv_data;
475 int ret;
476
477 1294 bytestream2_init(&s->gb, avpkt->data, avpkt->size);
478
479
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 1294 if (avpkt->size >= 6) {
480
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 2588 s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||
481
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 1294 memcmp(avpkt->data, gif89a_sig, 6) == 0;
482 } else {
483 ✗ s->keyframe = 0;
484 }
485
486
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 1294 if (s->keyframe) {
487 13 s->keyframe_ok = 0;
488 13 s->gce_prev_disposal = GCE_DISPOSAL_NONE;
489
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 13 if ((ret = gif_read_header1(s)) < 0)
490 ✗ return ret;
491
492
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 13 if ((ret = ff_set_dimensions(avctx, s->screen_width, s->screen_height)) < 0)
493 ✗ return ret;
494
495 13 av_frame_unref(s->frame);
496 13 av_fast_malloc(&s->idx_line, &s->idx_line_size, s->screen_width);
497
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 13 if (!s->idx_line)
498 ✗ return AVERROR(ENOMEM);
499
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 1281 } else if (!s->keyframe_ok) {
500 ✗ av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");
501 ✗ return AVERROR_INVALIDDATA;
502 }
503
504 1294 ret = ff_reget_buffer(avctx, s->frame, 0);
505
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 1294 if (ret < 0)
506 ✗ return ret;
507
508 1294 ret = gif_parse_next_image(s, s->frame);
509
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 1294 if (ret < 0)
510 ✗ return ret;
511
512
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 1294 if ((ret = av_frame_ref(rframe, s->frame)) < 0)
513 ✗ return ret;
514
515
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 1294 rframe->pict_type = s->keyframe ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
516 1294 rframe->flags = AV_FRAME_FLAG_KEY * s->keyframe;
517 1294 s->keyframe_ok |= !!s->keyframe;
518
519 1294 *got_frame = 1;
520
521 1294 return bytestream2_tell(&s->gb);
522 }
523
524 28 static av_cold int gif_decode_close(AVCodecContext *avctx)
525 {
526 28 GifState *s = avctx->priv_data;
527
528 28 ff_lzw_decode_close(&s->lzw);
529 28 av_frame_free(&s->frame);
530 28 av_freep(&s->idx_line);
531 28 av_freep(&s->stored_img);
532
533 28 return 0;
534 }
535
536 static const AVOption options[] = {
537 { "trans_color", "color value (ARGB) that is used instead of transparent color",
538 offsetof(GifState, trans_color), AV_OPT_TYPE_INT,
539 {.i64 = GIF_TRANSPARENT_COLOR}, 0, 0xffffffff,
540 AV_OPT_FLAG_DECODING_PARAM|AV_OPT_FLAG_VIDEO_PARAM },
541 { NULL },
542 };
543
544 static const AVClass decoder_class = {
545 .class_name = "gif decoder",
546 .item_name = av_default_item_name,
547 .option = options,
548 .version = LIBAVUTIL_VERSION_INT,
549 .category = AV_CLASS_CATEGORY_DECODER,
550 };
551
552 const FFCodec ff_gif_decoder = {
553 .p.name = "gif",
554 CODEC_LONG_NAME("GIF (Graphics Interchange Format)"),
555 .p.type = AVMEDIA_TYPE_VIDEO,
556 .p.id = AV_CODEC_ID_GIF,
557 .priv_data_size = sizeof(GifState),
558 .init = gif_decode_init,
559 .close = gif_decode_close,
560 FF_CODEC_DECODE_CB(gif_decode_frame),
561 .p.capabilities = AV_CODEC_CAP_DR1,
562 .caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
563 .p.priv_class = &decoder_class,
564 };
565