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gifdec.c
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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;
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 (left + width > s->screen_width ||
183  top + height > s->screen_height) {
184  av_log(s->avctx, AV_LOG_ERROR, "image is outside the screen dimensions.\n");
185  return AVERROR_INVALIDDATA;
186  }
187  if (width <= 0 || height <= 0) {
188  av_log(s->avctx, AV_LOG_ERROR, "Invalid image dimensions.\n");
189  return AVERROR_INVALIDDATA;
190  }
191 
192  /* process disposal method */
194  gif_fill_rect(frame, s->stored_bg_color, s->gce_l, s->gce_t, s->gce_w, s->gce_h);
195  } else if (s->gce_prev_disposal == GCE_DISPOSAL_RESTORE) {
196  gif_copy_img_rect(s->stored_img, (uint32_t *)frame->data[0],
197  frame->linesize[0] / sizeof(uint32_t), s->gce_l, s->gce_t, s->gce_w, s->gce_h);
198  }
199 
201 
202  if (s->gce_disposal != GCE_DISPOSAL_NONE) {
203  s->gce_l = left; s->gce_t = top;
204  s->gce_w = width; s->gce_h = height;
205 
207  if (s->transparent_color_index >= 0)
209  else
210  s->stored_bg_color = s->bg_color;
211  } else if (s->gce_disposal == GCE_DISPOSAL_RESTORE) {
212  av_fast_malloc(&s->stored_img, &s->stored_img_size, frame->linesize[0] * frame->height);
213  if (!s->stored_img)
214  return AVERROR(ENOMEM);
215 
216  gif_copy_img_rect((uint32_t *)frame->data[0], s->stored_img,
217  frame->linesize[0] / sizeof(uint32_t), left, top, width, height);
218  }
219  }
220 
221  /* Expect at least 2 bytes: 1 for lzw code size and 1 for block size. */
222  if (bytestream2_get_bytes_left(&s->gb) < 2)
223  return AVERROR_INVALIDDATA;
224 
225  /* now get the image data */
226  code_size = bytestream2_get_byteu(&s->gb);
227  if ((ret = ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
229  av_log(s->avctx, AV_LOG_ERROR, "LZW init failed\n");
230  return ret;
231  }
232 
233  /* read all the image */
234  linesize = frame->linesize[0] / sizeof(uint32_t);
235  ptr1 = (uint32_t *)frame->data[0] + top * linesize + left;
236  ptr = ptr1;
237  pass = 0;
238  y1 = 0;
239  for (y = 0; y < height; y++) {
240  int count = ff_lzw_decode(s->lzw, s->idx_line, width);
241  if (count != width) {
242  if (count)
243  av_log(s->avctx, AV_LOG_ERROR, "LZW decode failed\n");
244  goto decode_tail;
245  }
246 
247  pr = ptr + width;
248 
249  for (px = ptr, idx = s->idx_line; px < pr; px++, idx++) {
250  if (*idx != s->transparent_color_index)
251  *px = pal[*idx];
252  }
253 
254  if (is_interleaved) {
255  switch(pass) {
256  default:
257  case 0:
258  case 1:
259  y1 += 8;
260  ptr += linesize * 8;
261  if (y1 >= height) {
262  y1 = pass ? 2 : 4;
263  ptr = ptr1 + linesize * y1;
264  pass++;
265  }
266  break;
267  case 2:
268  y1 += 4;
269  ptr += linesize * 4;
270  if (y1 >= height) {
271  y1 = 1;
272  ptr = ptr1 + linesize;
273  pass++;
274  }
275  break;
276  case 3:
277  y1 += 2;
278  ptr += linesize * 2;
279  break;
280  }
281  } else {
282  ptr += linesize;
283  }
284  }
285 
286  decode_tail:
287  /* read the garbage data until end marker is found */
289 
290  /* Graphic Control Extension's scope is single frame.
291  * Remove its influence. */
292  s->transparent_color_index = -1;
294 
295  return 0;
296 }
297 
299 {
300  int ext_code, ext_len, gce_flags, gce_transparent_index;
301 
302  /* There must be at least 2 bytes:
303  * 1 for extension label and 1 for extension length. */
304  if (bytestream2_get_bytes_left(&s->gb) < 2)
305  return AVERROR_INVALIDDATA;
306 
307  ext_code = bytestream2_get_byteu(&s->gb);
308  ext_len = bytestream2_get_byteu(&s->gb);
309 
310  av_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);
311 
312  switch(ext_code) {
313  case GIF_GCE_EXT_LABEL:
314  if (ext_len != 4)
315  goto discard_ext;
316 
317  /* We need at least 5 bytes more: 4 is for extension body
318  * and 1 for next block size. */
319  if (bytestream2_get_bytes_left(&s->gb) < 5)
320  return AVERROR_INVALIDDATA;
321 
322  gce_flags = bytestream2_get_byteu(&s->gb);
323  bytestream2_skipu(&s->gb, 2); // delay during which the frame is shown
324  gce_transparent_index = bytestream2_get_byteu(&s->gb);
325  if (gce_flags & 0x01)
326  s->transparent_color_index = gce_transparent_index;
327  else
328  s->transparent_color_index = -1;
329  s->gce_disposal = (gce_flags >> 2) & 0x7;
330 
331  av_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",
332  gce_flags,
334 
335  if (s->gce_disposal > 3) {
337  av_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);
338  }
339 
340  ext_len = bytestream2_get_byteu(&s->gb);
341  break;
342  }
343 
344  /* NOTE: many extension blocks can come after */
345  discard_ext:
346  while (ext_len) {
347  /* There must be at least ext_len bytes and 1 for next block size byte. */
348  if (bytestream2_get_bytes_left(&s->gb) < ext_len + 1)
349  return AVERROR_INVALIDDATA;
350 
351  bytestream2_skipu(&s->gb, ext_len);
352  ext_len = bytestream2_get_byteu(&s->gb);
353 
354  av_dlog(s->avctx, "ext_len1=%d\n", ext_len);
355  }
356  return 0;
357 }
358 
360 {
361  uint8_t sig[6];
362  int v, n;
363  int background_color_index;
364 
365  if (bytestream2_get_bytes_left(&s->gb) < 13)
366  return AVERROR_INVALIDDATA;
367 
368  /* read gif signature */
369  bytestream2_get_bufferu(&s->gb, sig, 6);
370  if (memcmp(sig, gif87a_sig, 6) &&
371  memcmp(sig, gif89a_sig, 6))
372  return AVERROR_INVALIDDATA;
373 
374  /* read screen header */
375  s->transparent_color_index = -1;
376  s->screen_width = bytestream2_get_le16u(&s->gb);
377  s->screen_height = bytestream2_get_le16u(&s->gb);
378 
379  v = bytestream2_get_byteu(&s->gb);
380  s->color_resolution = ((v & 0x70) >> 4) + 1;
381  s->has_global_palette = (v & 0x80);
382  s->bits_per_pixel = (v & 0x07) + 1;
383  background_color_index = bytestream2_get_byteu(&s->gb);
384  n = bytestream2_get_byteu(&s->gb);
385  if (n) {
386  s->avctx->sample_aspect_ratio.num = n + 15;
387  s->avctx->sample_aspect_ratio.den = 64;
388  }
389 
390  av_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
392  s->has_global_palette);
393 
394  if (s->has_global_palette) {
395  s->background_color_index = background_color_index;
396  n = 1 << s->bits_per_pixel;
397  if (bytestream2_get_bytes_left(&s->gb) < n * 3)
398  return AVERROR_INVALIDDATA;
399 
402  } else
403  s->background_color_index = -1;
404 
405  return 0;
406 }
407 
409 {
410  while (bytestream2_get_bytes_left(&s->gb) > 0) {
411  int code = bytestream2_get_byte(&s->gb);
412  int ret;
413 
414  av_log(s->avctx, AV_LOG_DEBUG, "code=%02x '%c'\n", code, code);
415 
416  switch (code) {
417  case GIF_IMAGE_SEPARATOR:
418  return gif_read_image(s, frame);
420  if ((ret = gif_read_extension(s)) < 0)
421  return ret;
422  break;
423  case GIF_TRAILER:
424  /* end of image */
425  return AVERROR_EOF;
426  default:
427  /* erroneous block label */
428  return AVERROR_INVALIDDATA;
429  }
430  }
431  return AVERROR_EOF;
432 }
433 
435 {
436  GifState *s = avctx->priv_data;
437 
438  s->avctx = avctx;
439 
440  avctx->pix_fmt = AV_PIX_FMT_RGB32;
441  s->frame = av_frame_alloc();
442  if (!s->frame)
443  return AVERROR(ENOMEM);
444  ff_lzw_decode_open(&s->lzw);
445  return 0;
446 }
447 
448 static int gif_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
449 {
450  GifState *s = avctx->priv_data;
451  int ret;
452 
453  bytestream2_init(&s->gb, avpkt->data, avpkt->size);
454 
455  s->frame->pts = avpkt->pts;
456  s->frame->pkt_pts = avpkt->pts;
457  s->frame->pkt_dts = avpkt->dts;
459 
460  if (avpkt->size >= 6) {
461  s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||
462  memcmp(avpkt->data, gif89a_sig, 6) == 0;
463  } else {
464  s->keyframe = 0;
465  }
466 
467  if (s->keyframe) {
468  s->keyframe_ok = 0;
470  if ((ret = gif_read_header1(s)) < 0)
471  return ret;
472 
473  if ((ret = ff_set_dimensions(avctx, s->screen_width, s->screen_height)) < 0)
474  return ret;
475 
476  av_frame_unref(s->frame);
477  if ((ret = ff_get_buffer(avctx, s->frame, 0)) < 0)
478  return ret;
479 
481  if (!s->idx_line)
482  return AVERROR(ENOMEM);
483 
485  s->frame->key_frame = 1;
486  s->keyframe_ok = 1;
487  } else {
488  if (!s->keyframe_ok) {
489  av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");
490  return AVERROR_INVALIDDATA;
491  }
492 
493  if ((ret = ff_reget_buffer(avctx, s->frame)) < 0)
494  return ret;
495 
497  s->frame->key_frame = 0;
498  }
499 
500  ret = gif_parse_next_image(s, s->frame);
501  if (ret < 0)
502  return ret;
503 
504  if ((ret = av_frame_ref(data, s->frame)) < 0)
505  return ret;
506  *got_frame = 1;
507 
508  return bytestream2_tell(&s->gb);
509 }
510 
512 {
513  GifState *s = avctx->priv_data;
514 
516  av_frame_free(&s->frame);
517  av_freep(&s->idx_line);
518  av_freep(&s->stored_img);
519 
520  return 0;
521 }
522 
523 static const AVOption options[] = {
524  { "trans_color", "color value (ARGB) that is used instead of transparent color",
525  offsetof(GifState, trans_color), AV_OPT_TYPE_INT,
526  {.i64 = GIF_TRANSPARENT_COLOR}, 0, 0xffffffff,
528  { NULL },
529 };
530 
531 static const AVClass decoder_class = {
532  .class_name = "gif decoder",
533  .item_name = av_default_item_name,
534  .option = options,
535  .version = LIBAVUTIL_VERSION_INT,
536  .category = AV_CLASS_CATEGORY_DECODER,
537 };
538 
540  .name = "gif",
541  .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
542  .type = AVMEDIA_TYPE_VIDEO,
543  .id = AV_CODEC_ID_GIF,
544  .priv_data_size = sizeof(GifState),
548  .capabilities = CODEC_CAP_DR1,
549  .priv_class = &decoder_class,
550 };