FFmpeg: libavcodec/gifdec.c Source File

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gifdec.c

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1 /*

2 * GIF decoder

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 */

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"

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

38 typedef struct GifState {

39 const AVClass *class;

40 AVFrame *frame;

41 int screen_width;

42 int screen_height;

43 int has_global_palette;

44 int bits_per_pixel;

45 uint32_t bg_color;

46 int background_color_index;

47 int transparent_color_index;

48 int color_resolution;

49 /* intermediate buffer for storing color indices

50 * obtained from lzw-encoded data stream */

51 uint8_t *idx_line;

52 int idx_line_size;

54 /* after the frame is displayed, the disposal method is used */

55 int gce_prev_disposal;

56 int gce_disposal;

57 /* rectangle describing area that must be disposed */

58 int gce_l, gce_t, gce_w, gce_h;

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;

63 int stored_img_size;

64 int stored_bg_color;

66 GetByteContext gb;

67 /* LZW compatible decoder */

68 LZWState *lzw;

70 /* aux buffers */

71 uint32_t global_palette[256];

72 uint32_t local_palette[256];

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;

80 static void gif_read_palette(GifState *s, uint32_t *pal, int nb)

81 {

82 int i;

84 for (i = 0; i < nb; i++, pal++)

85 *pal = (0xffu << 24) | bytestream2_get_be24u(&s->gb);

86 }

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;

93 for (; p < p_end; p++)

94 *p = color;

95 }

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

131 static int gif_read_image(GifState *s, AVFrame *frame)

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 */

190 if (s->gce_prev_disposal == GCE_DISPOSAL_BACKGROUND) {

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

197 s->gce_prev_disposal = s->gce_disposal;

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

203 if (s->gce_disposal == GCE_DISPOSAL_BACKGROUND) {

204 if (s->transparent_color_index >= 0)

205 s->stored_bg_color = s->trans_color;

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,

225 bytestream2_get_bytes_left(&s->gb), FF_LZW_GIF)) < 0) {

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 */

281 ff_lzw_decode_tail(s->lzw);

282

283 /* Graphic Control Extension's scope is single frame.

284 * Remove its influence. */

285 s->transparent_color_index = -1;

286 s->gce_disposal = GCE_DISPOSAL_NONE;

287

288 return 0;

289 }

290

291 static int gif_read_extension(GifState *s)

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,

326 s->transparent_color_index, s->gce_disposal);

327

328 if (s->gce_disposal > 3) {

329 s->gce_disposal = GCE_DISPOSAL_NONE;

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

352 static int gif_read_header1(GifState *s)

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",

384 s->screen_width, s->screen_height, s->bits_per_pixel,

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

393 gif_read_palette(s, s->global_palette, n);

394 s->bg_color = s->global_palette[s->background_color_index];

395 } else

396 s->background_color_index = -1;

397

398 return 0;

399 }

400

401 static int gif_parse_next_image(GifState *s, AVFrame *frame)

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);

412 case GIF_EXTENSION_INTRODUCER:

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

427 static av_cold int gif_decode_init(AVCodecContext *avctx)

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;

451 av_frame_set_pkt_duration(s->frame, avpkt->duration);

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;

462 s->gce_prev_disposal = GCE_DISPOSAL_NONE;

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;

468 avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);

469

470 av_frame_unref(s->frame);

471 if ((ret = ff_get_buffer(avctx, s->frame, 0)) < 0)

472 return ret;

473

474 av_fast_malloc(&s->idx_line, &s->idx_line_size, s->screen_width);

475 if (!s->idx_line)

476 return AVERROR(ENOMEM);

477

478 s->frame->pict_type = AV_PICTURE_TYPE_I;

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

490 s->frame->pict_type = AV_PICTURE_TYPE_P;

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

505 static av_cold int gif_decode_close(AVCodecContext *avctx)

506 {

507 GifState *s = avctx->priv_data;

508

509 ff_lzw_decode_close(&s->lzw);

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,

521 AV_OPT_FLAG_DECODING_PARAM|AV_OPT_FLAG_VIDEO_PARAM },

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

533 AVCodec ff_gif_decoder = {

534 .name = "gif",

535 .type = AVMEDIA_TYPE_VIDEO,

536 .id = AV_CODEC_ID_GIF,

537 .priv_data_size = sizeof(GifState),

538 .init = gif_decode_init,

539 .close = gif_decode_close,

540 .decode = gif_decode_frame,

541 .capabilities = CODEC_CAP_DR1,

542 .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),

543 .priv_class = &decoder_class,

544 };

Generated on Wed Jul 10 2013 23:47:58 for FFmpeg by doxygen 1.8.2