3 * Copyright (c) 2003 Fabrice Bellard.
4 * Copyright (c) 2006 Baptiste Coudurier.
6 * This file is part of FFmpeg.
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26 #include "bytestream.h"
29 #define GCE_DISPOSAL_NONE 0
30 #define GCE_DISPOSAL_INPLACE 1
31 #define GCE_DISPOSAL_BACKGROUND 2
32 #define GCE_DISPOSAL_RESTORE 3
34 typedef struct GifState {
39 int background_color_index;
40 int transparent_color_index;
42 uint32_t *image_palette;
44 /* after the frame is displayed, the disposal method is used */
46 /* delay during which the frame is shown */
49 /* LZW compatible decoder */
50 const uint8_t *bytestream;
51 const uint8_t *bytestream_end;
55 uint8_t global_palette[256 * 3];
56 uint8_t local_palette[256 * 3];
58 AVCodecContext* avctx;
61 static const uint8_t gif87a_sig[6] = "GIF87a";
62 static const uint8_t gif89a_sig[6] = "GIF89a";
64 static int gif_read_image(GifState *s)
66 int left, top, width, height, bits_per_pixel, code_size, flags;
67 int is_interleaved, has_local_palette, y, pass, y1, linesize, n, i;
68 uint8_t *ptr, *spal, *palette, *ptr1;
70 left = bytestream_get_le16(&s->bytestream);
71 top = bytestream_get_le16(&s->bytestream);
72 width = bytestream_get_le16(&s->bytestream);
73 height = bytestream_get_le16(&s->bytestream);
74 flags = bytestream_get_byte(&s->bytestream);
75 is_interleaved = flags & 0x40;
76 has_local_palette = flags & 0x80;
77 bits_per_pixel = (flags & 0x07) + 1;
79 dprintf(s->avctx, "gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
82 if (has_local_palette) {
83 bytestream_get_buffer(&s->bytestream, s->local_palette, 3 * (1 << bits_per_pixel));
84 palette = s->local_palette;
86 palette = s->global_palette;
87 bits_per_pixel = s->bits_per_pixel;
90 /* verify that all the image is inside the screen dimensions */
91 if (left + width > s->screen_width ||
92 top + height > s->screen_height)
93 return AVERROR(EINVAL);
95 /* build the palette */
96 n = (1 << bits_per_pixel);
98 for(i = 0; i < n; i++) {
99 s->image_palette[i] = (0xff << 24) | AV_RB24(spal);
103 s->image_palette[i] = (0xff << 24);
104 /* handle transparency */
105 if (s->transparent_color_index >= 0)
106 s->image_palette[s->transparent_color_index] = 0;
108 /* now get the image data */
109 code_size = bytestream_get_byte(&s->bytestream);
110 ff_lzw_decode_init(s->lzw, code_size, s->bytestream,
111 s->bytestream_end - s->bytestream, FF_LZW_GIF);
113 /* read all the image */
114 linesize = s->picture.linesize[0];
115 ptr1 = s->picture.data[0] + top * linesize + left;
119 for (y = 0; y < height; y++) {
120 ff_lzw_decode(s->lzw, ptr, width);
121 if (is_interleaved) {
130 ptr = ptr1 + linesize * y1;
139 ptr = ptr1 + linesize;
152 /* read the garbage data until end marker is found */
153 ff_lzw_decode_tail(s->lzw);
154 s->bytestream = ff_lzw_cur_ptr(s->lzw);
158 static int gif_read_extension(GifState *s)
160 int ext_code, ext_len, i, gce_flags, gce_transparent_index;
163 ext_code = bytestream_get_byte(&s->bytestream);
164 ext_len = bytestream_get_byte(&s->bytestream);
166 dprintf(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
172 s->transparent_color_index = -1;
173 gce_flags = bytestream_get_byte(&s->bytestream);
174 s->gce_delay = bytestream_get_le16(&s->bytestream);
175 gce_transparent_index = bytestream_get_byte(&s->bytestream);
176 if (gce_flags & 0x01)
177 s->transparent_color_index = gce_transparent_index;
179 s->transparent_color_index = -1;
180 s->gce_disposal = (gce_flags >> 2) & 0x7;
182 dprintf(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
183 gce_flags, s->gce_delay,
184 s->transparent_color_index, s->gce_disposal);
186 ext_len = bytestream_get_byte(&s->bytestream);
190 /* NOTE: many extension blocks can come after */
192 while (ext_len != 0) {
193 for (i = 0; i < ext_len; i++)
194 bytestream_get_byte(&s->bytestream);
195 ext_len = bytestream_get_byte(&s->bytestream);
197 dprintf(s->avctx, "gif: ext_len1=%d\n", ext_len);
203 static int gif_read_header1(GifState *s)
207 int has_global_palette;
209 if (s->bytestream_end < s->bytestream + 13)
212 /* read gif signature */
213 bytestream_get_buffer(&s->bytestream, sig, 6);
214 if (memcmp(sig, gif87a_sig, 6) != 0 &&
215 memcmp(sig, gif89a_sig, 6) != 0)
218 /* read screen header */
219 s->transparent_color_index = -1;
220 s->screen_width = bytestream_get_le16(&s->bytestream);
221 s->screen_height = bytestream_get_le16(&s->bytestream);
222 if( (unsigned)s->screen_width > 32767
223 || (unsigned)s->screen_height > 32767){
224 av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
228 v = bytestream_get_byte(&s->bytestream);
229 s->color_resolution = ((v & 0x70) >> 4) + 1;
230 has_global_palette = (v & 0x80);
231 s->bits_per_pixel = (v & 0x07) + 1;
232 s->background_color_index = bytestream_get_byte(&s->bytestream);
233 bytestream_get_byte(&s->bytestream); /* ignored */
235 dprintf(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
236 s->screen_width, s->screen_height, s->bits_per_pixel,
239 if (has_global_palette) {
240 n = 1 << s->bits_per_pixel;
241 if (s->bytestream_end < s->bytestream + n * 3)
243 bytestream_get_buffer(&s->bytestream, s->global_palette, n * 3);
248 static int gif_parse_next_image(GifState *s)
250 while (s->bytestream < s->bytestream_end) {
251 int code = bytestream_get_byte(&s->bytestream);
253 dprintf(s->avctx, "gif: code=%02x '%c'\n", code, code);
257 return gif_read_image(s);
259 if (gif_read_extension(s) < 0)
265 /* error or erroneous EOF */
272 static av_cold int gif_decode_init(AVCodecContext *avctx)
274 GifState *s = avctx->priv_data;
278 avcodec_get_frame_defaults(&s->picture);
279 avctx->coded_frame= &s->picture;
280 s->picture.data[0] = NULL;
281 ff_lzw_decode_open(&s->lzw);
285 static int gif_decode_frame(AVCodecContext *avctx, void *data, int *data_size, const uint8_t *buf, int buf_size)
287 GifState *s = avctx->priv_data;
288 AVFrame *picture = data;
292 s->bytestream_end = buf + buf_size;
293 if (gif_read_header1(s) < 0)
296 avctx->pix_fmt = PIX_FMT_PAL8;
297 if (avcodec_check_dimensions(avctx, s->screen_width, s->screen_height))
299 avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);
301 if (s->picture.data[0])
302 avctx->release_buffer(avctx, &s->picture);
303 if (avctx->get_buffer(avctx, &s->picture) < 0) {
304 av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
307 s->image_palette = (uint32_t *)s->picture.data[1];
308 ret = gif_parse_next_image(s);
312 *picture = s->picture;
313 *data_size = sizeof(AVPicture);
314 return s->bytestream - buf;
317 static av_cold int gif_decode_close(AVCodecContext *avctx)
319 GifState *s = avctx->priv_data;
321 ff_lzw_decode_close(&s->lzw);
322 if(s->picture.data[0])
323 avctx->release_buffer(avctx, &s->picture);
327 AVCodec gif_decoder = {
336 .long_name = "GIF (Graphics Interchange Format)",