3 * Copyright (c) 2003 Fabrice Bellard.
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21 int gif_write(ByteIOContext *pb, AVImageInfo *info);
26 #define SIZTABLE (1<<MAXBITS)
28 #define GCE_DISPOSAL_NONE 0
29 #define GCE_DISPOSAL_INPLACE 1
30 #define GCE_DISPOSAL_BACKGROUND 2
31 #define GCE_DISPOSAL_RESTORE 3
33 typedef struct GifState {
37 int background_color_index;
38 int transparent_color_index;
42 uint32_t *image_palette;
45 /* after the frame is displayed, the disposal method is used */
47 /* delay during which the frame is shown */
50 /* LZW compatible decoder */
57 int cursize; /* The current code size */
62 int newcodes; /* First available code */
63 int top_slot; /* Highest code for current size */
64 int slot; /* Last read code */
67 uint8_t stack[SIZTABLE];
68 uint8_t suffix[SIZTABLE];
69 uint16_t prefix[SIZTABLE];
72 uint8_t global_palette[256 * 3];
73 uint8_t local_palette[256 * 3];
78 static const uint8_t gif87a_sig[6] = "GIF87a";
79 static const uint8_t gif89a_sig[6] = "GIF89a";
81 static const uint16_t mask[17] =
83 0x0000, 0x0001, 0x0003, 0x0007,
84 0x000F, 0x001F, 0x003F, 0x007F,
85 0x00FF, 0x01FF, 0x03FF, 0x07FF,
86 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF
89 /* Probe gif video format or gif image format. The current heuristic
90 supposes the gif87a is always a single image. For gif89a, we
91 consider it as a video only if a GCE extension is present in the
93 static int gif_video_probe(AVProbeData * pd)
95 const uint8_t *p, *p_end;
96 int bits_per_pixel, has_global_palette, ext_code, ext_len;
97 int gce_flags, gce_disposal;
99 if (pd->buf_size < 24 ||
100 memcmp(pd->buf, gif89a_sig, 6) != 0)
102 p_end = pd->buf + pd->buf_size;
104 bits_per_pixel = (p[4] & 0x07) + 1;
105 has_global_palette = (p[4] & 0x80);
107 if (has_global_palette)
108 p += (1 << bits_per_pixel) * 3;
121 if (ext_code == 0xf9) {
124 /* if GCE extension found with gce_disposal != 0: it is
125 likely to be an animation */
127 gce_disposal = (gce_flags >> 2) & 0x7;
128 if (gce_disposal != 0)
129 return AVPROBE_SCORE_MAX;
145 static int gif_image_probe(AVProbeData * pd)
147 if (pd->buf_size >= 24 &&
148 (memcmp(pd->buf, gif87a_sig, 6) == 0 ||
149 memcmp(pd->buf, gif89a_sig, 6) == 0))
150 return AVPROBE_SCORE_MAX - 1;
156 static void GLZWDecodeInit(GifState * s, int csize)
167 s->cursize = s->codesize + 1;
168 s->curmask = mask[s->cursize];
169 s->top_slot = 1 << s->cursize;
170 s->clear_code = 1 << s->codesize;
171 s->end_code = s->clear_code + 1;
172 s->slot = s->newcodes = s->clear_code + 2;
178 static inline int GetCode(GifState * s)
183 while (s->bbits < s->cursize) {
185 if (ptr >= s->ebuf) {
186 if (!s->eob_reached) {
187 sizbuf = get_byte(s->f);
188 s->ebuf = s->buf + sizbuf;
191 get_buffer(s->f, s->buf, sizbuf);
198 s->bbuf |= ptr[0] << s->bbits;
203 c = s->bbuf & s->curmask;
204 s->bbuf >>= s->cursize;
205 s->bbits -= s->cursize;
209 /* NOTE: the algorithm here is inspired from the LZW GIF decoder
210 written by Steven A. Bennett in 1987. */
211 /* return the number of byte decoded */
212 static int GLZWDecode(GifState * s, uint8_t * buf, int len)
214 int l, c, code, oc, fc;
225 while (sp > s->stack) {
233 if (c == s->end_code) {
236 } else if (c == s->clear_code) {
237 s->cursize = s->codesize + 1;
238 s->curmask = mask[s->cursize];
239 s->slot = s->newcodes;
240 s->top_slot = 1 << s->cursize;
241 while ((c = GetCode(s)) == s->clear_code);
242 if (c == s->end_code) {
255 if (code >= s->slot) {
259 while (code >= s->newcodes) {
260 *sp++ = s->suffix[code];
261 code = s->prefix[code];
264 if (s->slot < s->top_slot) {
265 s->suffix[s->slot] = fc = code;
266 s->prefix[s->slot++] = oc;
269 if (s->slot >= s->top_slot) {
270 if (s->cursize < MAXBITS) {
272 s->curmask = mask[++s->cursize];
275 while (sp > s->stack) {
289 static int gif_read_image(GifState *s)
291 ByteIOContext *f = s->f;
292 int left, top, width, height, bits_per_pixel, code_size, flags;
293 int is_interleaved, has_local_palette, y, x, pass, y1, linesize, n, i;
294 uint8_t *ptr, *line, *d, *spal, *palette, *sptr, *ptr1;
299 height = get_le16(f);
301 is_interleaved = flags & 0x40;
302 has_local_palette = flags & 0x80;
303 bits_per_pixel = (flags & 0x07) + 1;
305 printf("gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
308 if (has_local_palette) {
309 get_buffer(f, s->local_palette, 3 * (1 << bits_per_pixel));
310 palette = s->local_palette;
312 palette = s->global_palette;
313 bits_per_pixel = s->bits_per_pixel;
316 /* verify that all the image is inside the screen dimensions */
317 if (left + width > s->screen_width ||
318 top + height > s->screen_height)
321 /* build the palette */
322 if (s->pix_fmt == PIX_FMT_RGB24) {
323 line = av_malloc(width);
327 n = (1 << bits_per_pixel);
329 for(i = 0; i < n; i++) {
330 s->image_palette[i] = (0xff << 24) |
331 (spal[0] << 16) | (spal[1] << 8) | (spal[2]);
335 s->image_palette[i] = (0xff << 24);
336 /* handle transparency */
337 if (s->transparent_color_index >= 0)
338 s->image_palette[s->transparent_color_index] = 0;
342 /* now get the image data */
344 code_size = get_byte(f);
345 GLZWDecodeInit(s, code_size);
347 /* read all the image */
348 linesize = s->image_linesize;
349 ptr1 = s->image_buf + top * linesize + (left * 3);
353 for (y = 0; y < height; y++) {
354 if (s->pix_fmt == PIX_FMT_RGB24) {
355 /* transcode to RGB24 */
356 GLZWDecode(s, line, width);
359 for(x = 0; x < width; x++) {
360 spal = palette + sptr[0] * 3;
368 GLZWDecode(s, ptr, width);
370 if (is_interleaved) {
380 ptr = ptr1 + linesize * 4;
382 ptr = ptr1 + linesize * 2;
391 ptr = ptr1 + linesize;
406 /* read the garbage data until end marker is found */
407 while (!s->eob_reached)
412 static int gif_read_extension(GifState *s)
414 ByteIOContext *f = s->f;
415 int ext_code, ext_len, i, gce_flags, gce_transparent_index;
418 ext_code = get_byte(f);
419 ext_len = get_byte(f);
421 printf("gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
427 s->transparent_color_index = -1;
428 gce_flags = get_byte(f);
429 s->gce_delay = get_le16(f);
430 gce_transparent_index = get_byte(f);
431 if (gce_flags & 0x01)
432 s->transparent_color_index = gce_transparent_index;
434 s->transparent_color_index = -1;
435 s->gce_disposal = (gce_flags >> 2) & 0x7;
437 printf("gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
438 gce_flags, s->gce_delay,
439 s->transparent_color_index, s->gce_disposal);
441 ext_len = get_byte(f);
445 /* NOTE: many extension blocks can come after */
447 while (ext_len != 0) {
448 for (i = 0; i < ext_len; i++)
450 ext_len = get_byte(f);
452 printf("gif: ext_len1=%d\n", ext_len);
458 static int gif_read_header1(GifState *s)
460 ByteIOContext *f = s->f;
463 int has_global_palette;
465 /* read gif signature */
466 ret = get_buffer(f, sig, 6);
469 if (memcmp(sig, gif87a_sig, 6) != 0 &&
470 memcmp(sig, gif89a_sig, 6) != 0)
473 /* read screen header */
474 s->transparent_color_index = -1;
475 s->screen_width = get_le16(f);
476 s->screen_height = get_le16(f);
478 s->color_resolution = ((v & 0x70) >> 4) + 1;
479 has_global_palette = (v & 0x80);
480 s->bits_per_pixel = (v & 0x07) + 1;
481 s->background_color_index = get_byte(f);
482 get_byte(f); /* ignored */
484 printf("gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
485 s->screen_width, s->screen_height, s->bits_per_pixel,
488 if (has_global_palette) {
489 n = 1 << s->bits_per_pixel;
490 get_buffer(f, s->global_palette, n * 3);
495 static int gif_parse_next_image(GifState *s)
497 ByteIOContext *f = s->f;
503 printf("gif: code=%02x '%c'\n", code, code);
507 if (gif_read_image(s) < 0)
516 if (gif_read_extension(s) < 0)
521 /* error or errneous EOF */
530 static int gif_read_header(AVFormatContext * s1,
531 AVFormatParameters * ap)
533 GifState *s = s1->priv_data;
534 ByteIOContext *f = &s1->pb;
538 if (gif_read_header1(s) < 0)
541 /* allocate image buffer */
542 s->image_linesize = s->screen_width * 3;
543 s->image_buf = av_malloc(s->screen_height * s->image_linesize);
546 s->pix_fmt = PIX_FMT_RGB24;
547 /* now we are ready: build format streams */
548 st = av_new_stream(s1, 0);
552 st->codec.codec_type = CODEC_TYPE_VIDEO;
553 st->codec.codec_id = CODEC_ID_RAWVIDEO;
554 st->codec.frame_rate = 5;
555 st->codec.frame_rate_base = 1;
556 /* XXX: check if screen size is always valid */
557 st->codec.width = s->screen_width;
558 st->codec.height = s->screen_height;
559 st->codec.pix_fmt = PIX_FMT_RGB24;
563 static int gif_read_packet(AVFormatContext * s1,
566 GifState *s = s1->priv_data;
569 ret = gif_parse_next_image(s);
573 /* XXX: avoid copying */
574 if (av_new_packet(pkt, s->screen_width * s->screen_height * 3)) {
577 pkt->stream_index = 0;
578 memcpy(pkt->data, s->image_buf, s->screen_width * s->screen_height * 3);
582 static int gif_read_close(AVFormatContext *s1)
584 GifState *s = s1->priv_data;
585 av_free(s->image_buf);
589 /* read gif as image */
590 static int gif_read(ByteIOContext *f,
591 int (*alloc_cb)(void *opaque, AVImageInfo *info), void *opaque)
593 GifState s1, *s = &s1;
594 AVImageInfo info1, *info = &info1;
597 memset(s, 0, sizeof(GifState));
599 if (gif_read_header1(s) < 0)
601 info->width = s->screen_width;
602 info->height = s->screen_height;
603 info->pix_fmt = PIX_FMT_PAL8;
604 ret = alloc_cb(opaque, info);
607 s->image_buf = info->pict.data[0];
608 s->image_linesize = info->pict.linesize[0];
609 s->image_palette = (uint32_t *)info->pict.data[1];
611 if (gif_parse_next_image(s) < 0)
616 AVInputFormat gif_iformat =
627 AVImageFormat gif_image_format = {