FFmpeg: libavcodec/gifdec.c Source File

FFmpeg

[フレーム]

libavcodec

gifdec.c

Go to the documentation of this file.

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 LZWState *lzw;

69 /* aux buffers */

70 uint32_t global_palette[256];

71 uint32_t local_palette[256];

73 AVCodecContext *avctx;

74 int keyframe;

75 int keyframe_ok;

76 int trans_color; /**< color value that is used instead of transparent color */

77 } GifState;

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

80 {

81 int i;

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

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

85 }

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;

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

93 *p = color;

94 }

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

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

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 */

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

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

213 s->gce_prev_disposal = s->gce_disposal;

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

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

220 if (s->transparent_color_index >= 0)

221 s->stored_bg_color = s->trans_color;

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,

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

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 */

296 ff_lzw_decode_tail(s->lzw);

297

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

299 * Remove its influence. */

300 s->transparent_color_index = -1;

301 s->gce_disposal = GCE_DISPOSAL_NONE;

302

303 return 0;

304 }

305

306 static int gif_read_extension(GifState *s)

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,

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

342

343 if (s->gce_disposal > 3) {

344 s->gce_disposal = GCE_DISPOSAL_NONE;

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

367 static int gif_read_header1(GifState *s)

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",

399 s->screen_width, s->screen_height, s->bits_per_pixel,

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

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

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

410 } else

411 s->background_color_index = -1;

412

413 return 0;

414 }

415

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

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);

427 case GIF_EXTENSION_INTRODUCER:

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

442 static av_cold int gif_decode_init(AVCodecContext *avctx)

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;

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

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;

477 s->gce_prev_disposal = GCE_DISPOSAL_NONE;

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

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

489 if (!s->idx_line)

490 return AVERROR(ENOMEM);

491

492 s->frame->pict_type = AV_PICTURE_TYPE_I;

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

504 s->frame->pict_type = AV_PICTURE_TYPE_P;

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

519 static av_cold int gif_decode_close(AVCodecContext *avctx)

520 {

521 GifState *s = avctx->priv_data;

522

523 ff_lzw_decode_close(&s->lzw);

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,

535 AV_OPT_FLAG_DECODING_PARAM|AV_OPT_FLAG_VIDEO_PARAM },

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

547 AVCodec ff_gif_decoder = {

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),

553 .init = gif_decode_init,

554 .close = gif_decode_close,

555 .decode = gif_decode_frame,

556 .capabilities = CODEC_CAP_DR1,

557 .priv_class = &decoder_class,

558 };

Generated on Sun Mar 8 2015 02:34:52 for FFmpeg by doxygen 1.8.2