FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
gifdec.c
Go to the documentation of this file.
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/imgutils.h"
25 #include "libavutil/opt.h"
26 #include "avcodec.h"
27 #include "bytestream.h"
28 #include "internal.h"
29 #include "lzw.h"
30 #include "gif.h"
31 
32 /* This value is intentionally set to "transparent white" color.
33  * It is much better to have white background instead of black
34  * when gif image converted to format which not support transparency.
35  */
36 #define GIF_TRANSPARENT_COLOR 0x00ffffff
37 
38 typedef struct GifState {
39  const AVClass *class;
45  uint32_t bg_color;
49  /* intermediate buffer for storing color indices
50  * obtained from lzw-encoded data stream */
53 
54  /* after the frame is displayed, the disposal method is used */
57  /* rectangle describing area that must be disposed */
59  /* depending on disposal method we store either part of the image
60  * drawn on the canvas or background color that
61  * should be used upon disposal */
62  uint32_t * stored_img;
65 
68 
69  /* aux buffers */
70  uint32_t global_palette[256];
71  uint32_t local_palette[256];
72 
74  int keyframe;
76  int trans_color; /**< color value that is used instead of transparent color */
77 } GifState;
78 
79 static void gif_read_palette(GifState *s, uint32_t *pal, int nb)
80 {
81  int i;
82 
83  for (i = 0; i < nb; i++, pal++)
84  *pal = (0xffu << 24) | bytestream2_get_be24u(&s->gb);
85 }
86 
87 static void gif_fill(AVFrame *picture, uint32_t color)
88 {
89  uint32_t *p = (uint32_t *)picture->data[0];
90  uint32_t *p_end = p + (picture->linesize[0] / sizeof(uint32_t)) * picture->height;
91 
92  for (; p < p_end; p++)
93  *p = color;
94 }
95 
96 static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)
97 {
98  const int linesize = picture->linesize[0] / sizeof(uint32_t);
99  const uint32_t *py = (uint32_t *)picture->data[0] + t * linesize;
100  const uint32_t *pr, *pb = py + h * linesize;
101  uint32_t *px;
102 
103  for (; py < pb; py += linesize) {
104  px = (uint32_t *)py + l;
105  pr = px + w;
106 
107  for (; px < pr; px++)
108  *px = color;
109  }
110 }
111 
112 static void gif_copy_img_rect(const uint32_t *src, uint32_t *dst,
113  int linesize, int l, int t, int w, int h)
114 {
115  const int y_start = t * linesize;
116  const uint32_t *src_px,
117  *src_py = src + y_start,
118  *dst_py = dst + y_start;
119  const uint32_t *src_pb = src_py + h * linesize;
120  uint32_t *dst_px;
121 
122  for (; src_py < src_pb; src_py += linesize, dst_py += linesize) {
123  src_px = src_py + l;
124  dst_px = (uint32_t *)dst_py + l;
125 
126  memcpy(dst_px, src_px, w * sizeof(uint32_t));
127  }
128 }
129 
131 {
132  int left, top, width, height, bits_per_pixel, code_size, flags, pw;
133  int is_interleaved, has_local_palette, y, pass, y1, linesize, pal_size;
134  uint32_t *ptr, *pal, *px, *pr, *ptr1;
135  int ret;
136  uint8_t *idx;
137 
138  /* At least 9 bytes of Image Descriptor. */
139  if (bytestream2_get_bytes_left(&s->gb) < 9)
140  return AVERROR_INVALIDDATA;
141 
142  left = bytestream2_get_le16u(&s->gb);
143  top = bytestream2_get_le16u(&s->gb);
144  width = bytestream2_get_le16u(&s->gb);
145  height = bytestream2_get_le16u(&s->gb);
146  flags = bytestream2_get_byteu(&s->gb);
147  is_interleaved = flags & 0x40;
148  has_local_palette = flags & 0x80;
149  bits_per_pixel = (flags & 0x07) + 1;
150 
151  av_dlog(s->avctx, "image x=%d y=%d w=%d h=%d\n", left, top, width, height);
152 
153  if (has_local_palette) {
154  pal_size = 1 << bits_per_pixel;
155 
156  if (bytestream2_get_bytes_left(&s->gb) < pal_size * 3)
157  return AVERROR_INVALIDDATA;
158 
159  gif_read_palette(s, s->local_palette, pal_size);
160  pal = s->local_palette;
161  } else {
162  if (!s->has_global_palette) {
163  av_log(s->avctx, AV_LOG_ERROR, "picture doesn't have either global or local palette.\n");
164  return AVERROR_INVALIDDATA;
165  }
166 
167  pal = s->global_palette;
168  }
169 
170  if (s->keyframe) {
171  if (s->transparent_color_index == -1 && s->has_global_palette) {
172  /* transparency wasn't set before the first frame, fill with background color */
173  gif_fill(frame, s->bg_color);
174  } else {
175  /* otherwise fill with transparent color.
176  * this is necessary since by default picture filled with 0x80808080. */
177  gif_fill(frame, s->trans_color);
178  }
179  }
180 
181  /* verify that all the image is inside the screen dimensions */
182  if (!width || width > s->screen_width || left >= s->screen_width) {
183  av_log(s->avctx, AV_LOG_ERROR, "Invalid image width.\n");
184  return AVERROR_INVALIDDATA;
185  }
186  if (!height || height > s->screen_height || top >= s->screen_height) {
187  av_log(s->avctx, AV_LOG_ERROR, "Invalid image height.\n");
188  return AVERROR_INVALIDDATA;
189  }
190  if (left + width > s->screen_width) {
191  /* width must be kept around to avoid lzw vs line desync */
192  pw = s->screen_width - left;
193  av_log(s->avctx, AV_LOG_WARNING, "Image too wide by %d, truncating.\n",
194  left + width - s->screen_width);
195  } else {
196  pw = width;
197  }
198  if (top + height > s->screen_height) {
199  /* we don't care about the extra invisible lines */
200  av_log(s->avctx, AV_LOG_WARNING, "Image too high by %d, truncating.\n",
201  top + height - s->screen_height);
202  height = s->screen_height - top;
203  }
204 
205  /* process disposal method */
207  gif_fill_rect(frame, s->stored_bg_color, s->gce_l, s->gce_t, s->gce_w, s->gce_h);
208  } else if (s->gce_prev_disposal == GCE_DISPOSAL_RESTORE) {
209  gif_copy_img_rect(s->stored_img, (uint32_t *)frame->data[0],
210  frame->linesize[0] / sizeof(uint32_t), s->gce_l, s->gce_t, s->gce_w, s->gce_h);
211  }
212 
214 
215  if (s->gce_disposal != GCE_DISPOSAL_NONE) {
216  s->gce_l = left; s->gce_t = top;
217  s->gce_w = pw; s->gce_h = height;
218 
220  if (s->transparent_color_index >= 0)
222  else
223  s->stored_bg_color = s->bg_color;
224  } else if (s->gce_disposal == GCE_DISPOSAL_RESTORE) {
225  av_fast_malloc(&s->stored_img, &s->stored_img_size, frame->linesize[0] * frame->height);
226  if (!s->stored_img)
227  return AVERROR(ENOMEM);
228 
229  gif_copy_img_rect((uint32_t *)frame->data[0], s->stored_img,
230  frame->linesize[0] / sizeof(uint32_t), left, top, pw, height);
231  }
232  }
233 
234  /* Expect at least 2 bytes: 1 for lzw code size and 1 for block size. */
235  if (bytestream2_get_bytes_left(&s->gb) < 2)
236  return AVERROR_INVALIDDATA;
237 
238  /* now get the image data */
239  code_size = bytestream2_get_byteu(&s->gb);
240  if ((ret = ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
242  av_log(s->avctx, AV_LOG_ERROR, "LZW init failed\n");
243  return ret;
244  }
245 
246  /* read all the image */
247  linesize = frame->linesize[0] / sizeof(uint32_t);
248  ptr1 = (uint32_t *)frame->data[0] + top * linesize + left;
249  ptr = ptr1;
250  pass = 0;
251  y1 = 0;
252  for (y = 0; y < height; y++) {
253  int count = ff_lzw_decode(s->lzw, s->idx_line, width);
254  if (count != width) {
255  if (count)
256  av_log(s->avctx, AV_LOG_ERROR, "LZW decode failed\n");
257  goto decode_tail;
258  }
259 
260  pr = ptr + pw;
261 
262  for (px = ptr, idx = s->idx_line; px < pr; px++, idx++) {
263  if (*idx != s->transparent_color_index)
264  *px = pal[*idx];
265  }
266 
267  if (is_interleaved) {
268  switch(pass) {
269  default:
270  case 0:
271  case 1:
272  y1 += 8;
273  ptr += linesize * 8;
274  break;
275  case 2:
276  y1 += 4;
277  ptr += linesize * 4;
278  break;
279  case 3:
280  y1 += 2;
281  ptr += linesize * 2;
282  break;
283  }
284  while (y1 >= height) {
285  y1 = 4 >> pass;
286  ptr = ptr1 + linesize * y1;
287  pass++;
288  }
289  } else {
290  ptr += linesize;
291  }
292  }
293 
294  decode_tail:
295  /* read the garbage data until end marker is found */
297 
298  /* Graphic Control Extension's scope is single frame.
299  * Remove its influence. */
300  s->transparent_color_index = -1;
302 
303  return 0;
304 }
305 
307 {
308  int ext_code, ext_len, gce_flags, gce_transparent_index;
309 
310  /* There must be at least 2 bytes:
311  * 1 for extension label and 1 for extension length. */
312  if (bytestream2_get_bytes_left(&s->gb) < 2)
313  return AVERROR_INVALIDDATA;
314 
315  ext_code = bytestream2_get_byteu(&s->gb);
316  ext_len = bytestream2_get_byteu(&s->gb);
317 
318  av_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);
319 
320  switch(ext_code) {
321  case GIF_GCE_EXT_LABEL:
322  if (ext_len != 4)
323  goto discard_ext;
324 
325  /* We need at least 5 bytes more: 4 is for extension body
326  * and 1 for next block size. */
327  if (bytestream2_get_bytes_left(&s->gb) < 5)
328  return AVERROR_INVALIDDATA;
329 
330  gce_flags = bytestream2_get_byteu(&s->gb);
331  bytestream2_skipu(&s->gb, 2); // delay during which the frame is shown
332  gce_transparent_index = bytestream2_get_byteu(&s->gb);
333  if (gce_flags & 0x01)
334  s->transparent_color_index = gce_transparent_index;
335  else
336  s->transparent_color_index = -1;
337  s->gce_disposal = (gce_flags >> 2) & 0x7;
338 
339  av_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",
340  gce_flags,
342 
343  if (s->gce_disposal > 3) {
345  av_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);
346  }
347 
348  ext_len = bytestream2_get_byteu(&s->gb);
349  break;
350  }
351 
352  /* NOTE: many extension blocks can come after */
353  discard_ext:
354  while (ext_len) {
355  /* There must be at least ext_len bytes and 1 for next block size byte. */
356  if (bytestream2_get_bytes_left(&s->gb) < ext_len + 1)
357  return AVERROR_INVALIDDATA;
358 
359  bytestream2_skipu(&s->gb, ext_len);
360  ext_len = bytestream2_get_byteu(&s->gb);
361 
362  av_dlog(s->avctx, "ext_len1=%d\n", ext_len);
363  }
364  return 0;
365 }
366 
368 {
369  uint8_t sig[6];
370  int v, n;
371  int background_color_index;
372 
373  if (bytestream2_get_bytes_left(&s->gb) < 13)
374  return AVERROR_INVALIDDATA;
375 
376  /* read gif signature */
377  bytestream2_get_bufferu(&s->gb, sig, 6);
378  if (memcmp(sig, gif87a_sig, 6) &&
379  memcmp(sig, gif89a_sig, 6))
380  return AVERROR_INVALIDDATA;
381 
382  /* read screen header */
383  s->transparent_color_index = -1;
384  s->screen_width = bytestream2_get_le16u(&s->gb);
385  s->screen_height = bytestream2_get_le16u(&s->gb);
386 
387  v = bytestream2_get_byteu(&s->gb);
388  s->color_resolution = ((v & 0x70) >> 4) + 1;
389  s->has_global_palette = (v & 0x80);
390  s->bits_per_pixel = (v & 0x07) + 1;
391  background_color_index = bytestream2_get_byteu(&s->gb);
392  n = bytestream2_get_byteu(&s->gb);
393  if (n) {
394  s->avctx->sample_aspect_ratio.num = n + 15;
395  s->avctx->sample_aspect_ratio.den = 64;
396  }
397 
398  av_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
400  s->has_global_palette);
401 
402  if (s->has_global_palette) {
403  s->background_color_index = background_color_index;
404  n = 1 << s->bits_per_pixel;
405  if (bytestream2_get_bytes_left(&s->gb) < n * 3)
406  return AVERROR_INVALIDDATA;
407 
410  } else
411  s->background_color_index = -1;
412 
413  return 0;
414 }
415 
417 {
418  while (bytestream2_get_bytes_left(&s->gb) > 0) {
419  int code = bytestream2_get_byte(&s->gb);
420  int ret;
421 
422  av_log(s->avctx, AV_LOG_DEBUG, "code=%02x '%c'\n", code, code);
423 
424  switch (code) {
425  case GIF_IMAGE_SEPARATOR:
426  return gif_read_image(s, frame);
428  if ((ret = gif_read_extension(s)) < 0)
429  return ret;
430  break;
431  case GIF_TRAILER:
432  /* end of image */
433  return AVERROR_EOF;
434  default:
435  /* erroneous block label */
436  return AVERROR_INVALIDDATA;
437  }
438  }
439  return AVERROR_EOF;
440 }
441 
443 {
444  GifState *s = avctx->priv_data;
445 
446  s->avctx = avctx;
447 
448  avctx->pix_fmt = AV_PIX_FMT_RGB32;
449  s->frame = av_frame_alloc();
450  if (!s->frame)
451  return AVERROR(ENOMEM);
452  ff_lzw_decode_open(&s->lzw);
453  return 0;
454 }
455 
456 static int gif_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
457 {
458  GifState *s = avctx->priv_data;
459  int ret;
460 
461  bytestream2_init(&s->gb, avpkt->data, avpkt->size);
462 
463  s->frame->pts = avpkt->pts;
464  s->frame->pkt_pts = avpkt->pts;
465  s->frame->pkt_dts = avpkt->dts;
467 
468  if (avpkt->size >= 6) {
469  s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||
470  memcmp(avpkt->data, gif89a_sig, 6) == 0;
471  } else {
472  s->keyframe = 0;
473  }
474 
475  if (s->keyframe) {
476  s->keyframe_ok = 0;
478  if ((ret = gif_read_header1(s)) < 0)
479  return ret;
480 
481  if ((ret = ff_set_dimensions(avctx, s->screen_width, s->screen_height)) < 0)
482  return ret;
483 
484  av_frame_unref(s->frame);
485  if ((ret = ff_get_buffer(avctx, s->frame, 0)) < 0)
486  return ret;
487 
489  if (!s->idx_line)
490  return AVERROR(ENOMEM);
491 
493  s->frame->key_frame = 1;
494  s->keyframe_ok = 1;
495  } else {
496  if (!s->keyframe_ok) {
497  av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");
498  return AVERROR_INVALIDDATA;
499  }
500 
501  if ((ret = ff_reget_buffer(avctx, s->frame)) < 0)
502  return ret;
503 
505  s->frame->key_frame = 0;
506  }
507 
508  ret = gif_parse_next_image(s, s->frame);
509  if (ret < 0)
510  return ret;
511 
512  if ((ret = av_frame_ref(data, s->frame)) < 0)
513  return ret;
514  *got_frame = 1;
515 
516  return bytestream2_tell(&s->gb);
517 }
518 
520 {
521  GifState *s = avctx->priv_data;
522 
524  av_frame_free(&s->frame);
525  av_freep(&s->idx_line);
526  av_freep(&s->stored_img);
527 
528  return 0;
529 }
530 
531 static const AVOption options[] = {
532  { "trans_color", "color value (ARGB) that is used instead of transparent color",
533  offsetof(GifState, trans_color), AV_OPT_TYPE_INT,
534  {.i64 = GIF_TRANSPARENT_COLOR}, 0, 0xffffffff,
536  { NULL },
537 };
538 
539 static const AVClass decoder_class = {
540  .class_name = "gif decoder",
541  .item_name = av_default_item_name,
542  .option = options,
543  .version = LIBAVUTIL_VERSION_INT,
544  .category = AV_CLASS_CATEGORY_DECODER,
545 };
546 
548  .name = "gif",
549  .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
550  .type = AVMEDIA_TYPE_VIDEO,
551  .id = AV_CODEC_ID_GIF,
552  .priv_data_size = sizeof(GifState),
556  .capabilities = CODEC_CAP_DR1,
557  .priv_class = &decoder_class,
558 };