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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 
67  /* LZW compatible decoder */
69 
70  /* aux buffers */
71  uint32_t global_palette[256];
72  uint32_t local_palette[256];
73 
75  int keyframe;
77  int trans_color; /**< color value that is used instead of transparent color */
78 } GifState;
79 
80 static void gif_read_palette(GifState *s, uint32_t *pal, int nb)
81 {
82  int i;
83 
84  for (i = 0; i < nb; i++, pal++)
85  *pal = (0xffu << 24) | bytestream2_get_be24u(&s->gb);
86 }
87 
88 static void gif_fill(AVFrame *picture, uint32_t color)
89 {
90  uint32_t *p = (uint32_t *)picture->data[0];
91  uint32_t *p_end = p + (picture->linesize[0] / sizeof(uint32_t)) * picture->height;
92 
93  for (; p < p_end; p++)
94  *p = color;
95 }
96 
97 static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)
98 {
99  const int linesize = picture->linesize[0] / sizeof(uint32_t);
100  const uint32_t *py = (uint32_t *)picture->data[0] + t * linesize;
101  const uint32_t *pr, *pb = py + h * linesize;
102  uint32_t *px;
103 
104  for (; py < pb; py += linesize) {
105  px = (uint32_t *)py + l;
106  pr = px + w;
107 
108  for (; px < pr; px++)
109  *px = color;
110  }
111 }
112 
113 static void gif_copy_img_rect(const uint32_t *src, uint32_t *dst,
114  int linesize, int l, int t, int w, int h)
115 {
116  const int y_start = t * linesize;
117  const uint32_t *src_px,
118  *src_py = src + y_start,
119  *dst_py = dst + y_start;
120  const uint32_t *src_pb = src_py + h * linesize;
121  uint32_t *dst_px;
122 
123  for (; src_py < src_pb; src_py += linesize, dst_py += linesize) {
124  src_px = src_py + l;
125  dst_px = (uint32_t *)dst_py + l;
126 
127  memcpy(dst_px, src_px, w * sizeof(uint32_t));
128  }
129 }
130 
132 {
133  int left, top, width, height, bits_per_pixel, code_size, flags;
134  int is_interleaved, has_local_palette, y, pass, y1, linesize, pal_size;
135  uint32_t *ptr, *pal, *px, *pr, *ptr1;
136  int ret;
137  uint8_t *idx;
138 
139  /* At least 9 bytes of Image Descriptor. */
140  if (bytestream2_get_bytes_left(&s->gb) < 9)
141  return AVERROR_INVALIDDATA;
142 
143  left = bytestream2_get_le16u(&s->gb);
144  top = bytestream2_get_le16u(&s->gb);
145  width = bytestream2_get_le16u(&s->gb);
146  height = bytestream2_get_le16u(&s->gb);
147  flags = bytestream2_get_byteu(&s->gb);
148  is_interleaved = flags & 0x40;
149  has_local_palette = flags & 0x80;
150  bits_per_pixel = (flags & 0x07) + 1;
151 
152  av_dlog(s->avctx, "image x=%d y=%d w=%d h=%d\n", left, top, width, height);
153 
154  if (has_local_palette) {
155  pal_size = 1 << bits_per_pixel;
156 
157  if (bytestream2_get_bytes_left(&s->gb) < pal_size * 3)
158  return AVERROR_INVALIDDATA;
159 
160  gif_read_palette(s, s->local_palette, pal_size);
161  pal = s->local_palette;
162  } else {
163  if (!s->has_global_palette) {
164  av_log(s->avctx, AV_LOG_ERROR, "picture doesn't have either global or local palette.\n");
165  return AVERROR_INVALIDDATA;
166  }
167 
168  pal = s->global_palette;
169  }
170 
171  if (s->keyframe) {
172  if (s->transparent_color_index == -1 && s->has_global_palette) {
173  /* transparency wasn't set before the first frame, fill with background color */
174  gif_fill(frame, s->bg_color);
175  } else {
176  /* otherwise fill with transparent color.
177  * this is necessary since by default picture filled with 0x80808080. */
178  gif_fill(frame, s->trans_color);
179  }
180  }
181 
182  /* verify that all the image is inside the screen dimensions */
183  if (left + width > s->screen_width ||
184  top + height > s->screen_height)
185  return AVERROR_INVALIDDATA;
186  if (width <= 0 || height <= 0)
187  return AVERROR_INVALIDDATA;
188 
189  /* process disposal method */
191  gif_fill_rect(frame, s->stored_bg_color, s->gce_l, s->gce_t, s->gce_w, s->gce_h);
192  } else if (s->gce_prev_disposal == GCE_DISPOSAL_RESTORE) {
193  gif_copy_img_rect(s->stored_img, (uint32_t *)frame->data[0],
194  frame->linesize[0] / sizeof(uint32_t), s->gce_l, s->gce_t, s->gce_w, s->gce_h);
195  }
196 
198 
199  if (s->gce_disposal != GCE_DISPOSAL_NONE) {
200  s->gce_l = left; s->gce_t = top;
201  s->gce_w = width; s->gce_h = height;
202 
204  if (s->transparent_color_index >= 0)
206  else
207  s->stored_bg_color = s->bg_color;
208  } else if (s->gce_disposal == GCE_DISPOSAL_RESTORE) {
209  av_fast_malloc(&s->stored_img, &s->stored_img_size, frame->linesize[0] * frame->height);
210  if (!s->stored_img)
211  return AVERROR(ENOMEM);
212 
213  gif_copy_img_rect((uint32_t *)frame->data[0], s->stored_img,
214  frame->linesize[0] / sizeof(uint32_t), left, top, width, height);
215  }
216  }
217 
218  /* Expect at least 2 bytes: 1 for lzw code size and 1 for block size. */
219  if (bytestream2_get_bytes_left(&s->gb) < 2)
220  return AVERROR_INVALIDDATA;
221 
222  /* now get the image data */
223  code_size = bytestream2_get_byteu(&s->gb);
224  if ((ret = ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
226  av_log(s->avctx, AV_LOG_ERROR, "LZW init failed\n");
227  return ret;
228  }
229 
230  /* read all the image */
231  linesize = frame->linesize[0] / sizeof(uint32_t);
232  ptr1 = (uint32_t *)frame->data[0] + top * linesize + left;
233  ptr = ptr1;
234  pass = 0;
235  y1 = 0;
236  for (y = 0; y < height; y++) {
237  if (ff_lzw_decode(s->lzw, s->idx_line, width) == 0)
238  goto decode_tail;
239 
240  pr = ptr + width;
241 
242  for (px = ptr, idx = s->idx_line; px < pr; px++, idx++) {
243  if (*idx != s->transparent_color_index)
244  *px = pal[*idx];
245  }
246 
247  if (is_interleaved) {
248  switch(pass) {
249  default:
250  case 0:
251  case 1:
252  y1 += 8;
253  ptr += linesize * 8;
254  if (y1 >= height) {
255  y1 = pass ? 2 : 4;
256  ptr = ptr1 + linesize * y1;
257  pass++;
258  }
259  break;
260  case 2:
261  y1 += 4;
262  ptr += linesize * 4;
263  if (y1 >= height) {
264  y1 = 1;
265  ptr = ptr1 + linesize;
266  pass++;
267  }
268  break;
269  case 3:
270  y1 += 2;
271  ptr += linesize * 2;
272  break;
273  }
274  } else {
275  ptr += linesize;
276  }
277  }
278 
279  decode_tail:
280  /* read the garbage data until end marker is found */
282 
283  /* Graphic Control Extension's scope is single frame.
284  * Remove its influence. */
285  s->transparent_color_index = -1;
287 
288  return 0;
289 }
290 
292 {
293  int ext_code, ext_len, gce_flags, gce_transparent_index;
294 
295  /* There must be at least 2 bytes:
296  * 1 for extension label and 1 for extension length. */
297  if (bytestream2_get_bytes_left(&s->gb) < 2)
298  return AVERROR_INVALIDDATA;
299 
300  ext_code = bytestream2_get_byteu(&s->gb);
301  ext_len = bytestream2_get_byteu(&s->gb);
302 
303  av_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);
304 
305  switch(ext_code) {
306  case GIF_GCE_EXT_LABEL:
307  if (ext_len != 4)
308  goto discard_ext;
309 
310  /* We need at least 5 bytes more: 4 is for extension body
311  * and 1 for next block size. */
312  if (bytestream2_get_bytes_left(&s->gb) < 5)
313  return AVERROR_INVALIDDATA;
314 
315  gce_flags = bytestream2_get_byteu(&s->gb);
316  bytestream2_skipu(&s->gb, 2); // delay during which the frame is shown
317  gce_transparent_index = bytestream2_get_byteu(&s->gb);
318  if (gce_flags & 0x01)
319  s->transparent_color_index = gce_transparent_index;
320  else
321  s->transparent_color_index = -1;
322  s->gce_disposal = (gce_flags >> 2) & 0x7;
323 
324  av_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",
325  gce_flags,
327 
328  if (s->gce_disposal > 3) {
330  av_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);
331  }
332 
333  ext_len = bytestream2_get_byteu(&s->gb);
334  break;
335  }
336 
337  /* NOTE: many extension blocks can come after */
338  discard_ext:
339  while (ext_len) {
340  /* There must be at least ext_len bytes and 1 for next block size byte. */
341  if (bytestream2_get_bytes_left(&s->gb) < ext_len + 1)
342  return AVERROR_INVALIDDATA;
343 
344  bytestream2_skipu(&s->gb, ext_len);
345  ext_len = bytestream2_get_byteu(&s->gb);
346 
347  av_dlog(s->avctx, "ext_len1=%d\n", ext_len);
348  }
349  return 0;
350 }
351 
353 {
354  uint8_t sig[6];
355  int v, n;
356  int background_color_index;
357 
358  if (bytestream2_get_bytes_left(&s->gb) < 13)
359  return AVERROR_INVALIDDATA;
360 
361  /* read gif signature */
362  bytestream2_get_bufferu(&s->gb, sig, 6);
363  if (memcmp(sig, gif87a_sig, 6) &&
364  memcmp(sig, gif89a_sig, 6))
365  return AVERROR_INVALIDDATA;
366 
367  /* read screen header */
368  s->transparent_color_index = -1;
369  s->screen_width = bytestream2_get_le16u(&s->gb);
370  s->screen_height = bytestream2_get_le16u(&s->gb);
371 
372  v = bytestream2_get_byteu(&s->gb);
373  s->color_resolution = ((v & 0x70) >> 4) + 1;
374  s->has_global_palette = (v & 0x80);
375  s->bits_per_pixel = (v & 0x07) + 1;
376  background_color_index = bytestream2_get_byteu(&s->gb);
377  n = bytestream2_get_byteu(&s->gb);
378  if (n) {
379  s->avctx->sample_aspect_ratio.num = n + 15;
380  s->avctx->sample_aspect_ratio.den = 64;
381  }
382 
383  av_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
385  s->has_global_palette);
386 
387  if (s->has_global_palette) {
388  s->background_color_index = background_color_index;
389  n = 1 << s->bits_per_pixel;
390  if (bytestream2_get_bytes_left(&s->gb) < n * 3)
391  return AVERROR_INVALIDDATA;
392 
395  } else
396  s->background_color_index = -1;
397 
398  return 0;
399 }
400 
402 {
403  while (bytestream2_get_bytes_left(&s->gb)) {
404  int code = bytestream2_get_byte(&s->gb);
405  int ret;
406 
407  av_log(s->avctx, AV_LOG_DEBUG, "code=%02x '%c'\n", code, code);
408 
409  switch (code) {
410  case GIF_IMAGE_SEPARATOR:
411  return gif_read_image(s, frame);
413  if ((ret = gif_read_extension(s)) < 0)
414  return ret;
415  break;
416  case GIF_TRAILER:
417  /* end of image */
418  return AVERROR_EOF;
419  default:
420  /* erroneous block label */
421  return AVERROR_INVALIDDATA;
422  }
423  }
424  return AVERROR_EOF;
425 }
426 
428 {
429  GifState *s = avctx->priv_data;
430 
431  s->avctx = avctx;
432 
433  avctx->pix_fmt = AV_PIX_FMT_RGB32;
434  s->frame = av_frame_alloc();
435  if (!s->frame)
436  return AVERROR(ENOMEM);
437  ff_lzw_decode_open(&s->lzw);
438  return 0;
439 }
440 
441 static int gif_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
442 {
443  GifState *s = avctx->priv_data;
444  int ret;
445 
446  bytestream2_init(&s->gb, avpkt->data, avpkt->size);
447 
448  s->frame->pts = avpkt->pts;
449  s->frame->pkt_pts = avpkt->pts;
450  s->frame->pkt_dts = avpkt->dts;
452 
453  if (avpkt->size >= 6) {
454  s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||
455  memcmp(avpkt->data, gif89a_sig, 6) == 0;
456  } else {
457  s->keyframe = 0;
458  }
459 
460  if (s->keyframe) {
461  s->keyframe_ok = 0;
463  if ((ret = gif_read_header1(s)) < 0)
464  return ret;
465 
466  if ((ret = av_image_check_size(s->screen_width, s->screen_height, 0, avctx)) < 0)
467  return ret;
469 
470  av_frame_unref(s->frame);
471  if ((ret = ff_get_buffer(avctx, s->frame, 0)) < 0)
472  return ret;
473 
475  if (!s->idx_line)
476  return AVERROR(ENOMEM);
477 
479  s->frame->key_frame = 1;
480  s->keyframe_ok = 1;
481  } else {
482  if (!s->keyframe_ok) {
483  av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");
484  return AVERROR_INVALIDDATA;
485  }
486 
487  if ((ret = ff_reget_buffer(avctx, s->frame)) < 0)
488  return ret;
489 
491  s->frame->key_frame = 0;
492  }
493 
494  ret = gif_parse_next_image(s, s->frame);
495  if (ret < 0)
496  return ret;
497 
498  if ((ret = av_frame_ref(data, s->frame)) < 0)
499  return ret;
500  *got_frame = 1;
501 
502  return avpkt->size;
503 }
504 
506 {
507  GifState *s = avctx->priv_data;
508 
510  av_frame_free(&s->frame);
511  av_freep(&s->idx_line);
512  av_freep(&s->stored_img);
513 
514  return 0;
515 }
516 
517 static const AVOption options[] = {
518  { "trans_color", "color value (ARGB) that is used instead of transparent color",
519  offsetof(GifState, trans_color), AV_OPT_TYPE_INT,
520  {.i64 = GIF_TRANSPARENT_COLOR}, 0, 0xffffffff,
522  { NULL },
523 };
524 
525 static const AVClass decoder_class = {
526  .class_name = "gif decoder",
527  .item_name = av_default_item_name,
528  .option = options,
529  .version = LIBAVUTIL_VERSION_INT,
530  .category = AV_CLASS_CATEGORY_DECODER,
531 };
532 
534  .name = "gif",
535  .type = AVMEDIA_TYPE_VIDEO,
536  .id = AV_CODEC_ID_GIF,
537  .priv_data_size = sizeof(GifState),
541  .capabilities = CODEC_CAP_DR1,
542  .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
543  .priv_class = &decoder_class,
544 };