1/* 2 * GIF decoder 3 * Copyright (c) 2003 Fabrice Bellard 4 * Copyright (c) 2006 Baptiste Coudurier 5 * 6 * This file is part of FFmpeg. 7 * 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. 12 * 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. 17 * 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 21 */ 22 23//#define DEBUG 24 25#include "avcodec.h" 26#include "bytestream.h" 27#include "lzw.h" 28 29#define GCE_DISPOSAL_NONE 0 30#define GCE_DISPOSAL_INPLACE 1 31#define GCE_DISPOSAL_BACKGROUND 2 32#define GCE_DISPOSAL_RESTORE 3 33 34typedef struct GifState { 35 AVFrame picture; 36 int screen_width; 37 int screen_height; 38 int bits_per_pixel; 39 int background_color_index; 40 int transparent_color_index; 41 int color_resolution; 42 uint32_t *image_palette; 43 44 /* after the frame is displayed, the disposal method is used */ 45 int gce_disposal; 46 /* delay during which the frame is shown */ 47 int gce_delay; 48 49 /* LZW compatible decoder */ 50 const uint8_t *bytestream; 51 const uint8_t *bytestream_end; 52 LZWState *lzw; 53 54 /* aux buffers */ 55 uint8_t global_palette[256 * 3]; 56 uint8_t local_palette[256 * 3]; 57 58 AVCodecContext* avctx; 59} GifState; 60 61static const uint8_t gif87a_sig[6] = "GIF87a"; 62static const uint8_t gif89a_sig[6] = "GIF89a"; 63 64static int gif_read_image(GifState *s) 65{ 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; 69 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; 78#ifdef DEBUG 79 dprintf(s->avctx, "gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height); 80#endif 81 82 if (has_local_palette) { 83 bytestream_get_buffer(&s->bytestream, s->local_palette, 3 * (1 << bits_per_pixel)); 84 palette = s->local_palette; 85 } else { 86 palette = s->global_palette; 87 bits_per_pixel = s->bits_per_pixel; 88 } 89 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); 94 95 /* build the palette */ 96 n = (1 << bits_per_pixel); 97 spal = palette; 98 for(i = 0; i < n; i++) { 99 s->image_palette[i] = (0xff << 24) | AV_RB24(spal); 100 spal += 3; 101 } 102 for(; i < 256; i++) 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; 107 108 /* 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); 112 113 /* read all the image */ 114 linesize = s->picture.linesize[0]; 115 ptr1 = s->picture.data[0] + top * linesize + left; 116 ptr = ptr1; 117 pass = 0; 118 y1 = 0; 119 for (y = 0; y < height; y++) { 120 ff_lzw_decode(s->lzw, ptr, width); 121 if (is_interleaved) { 122 switch(pass) { 123 default: 124 case 0: 125 case 1: 126 y1 += 8; 127 ptr += linesize * 8; 128 if (y1 >= height) { 129 y1 = pass ? 2 : 4; 130 ptr = ptr1 + linesize * y1; 131 pass++; 132 } 133 break; 134 case 2: 135 y1 += 4; 136 ptr += linesize * 4; 137 if (y1 >= height) { 138 y1 = 1; 139 ptr = ptr1 + linesize; 140 pass++; 141 } 142 break; 143 case 3: 144 y1 += 2; 145 ptr += linesize * 2; 146 break; 147 } 148 } else { 149 ptr += linesize; 150 } 151 } 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); 155 return 0; 156} 157 158static int gif_read_extension(GifState *s) 159{ 160 int ext_code, ext_len, i, gce_flags, gce_transparent_index; 161 162 /* extension */ 163 ext_code = bytestream_get_byte(&s->bytestream); 164 ext_len = bytestream_get_byte(&s->bytestream); 165#ifdef DEBUG 166 dprintf(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len); 167#endif 168 switch(ext_code) { 169 case 0xf9: 170 if (ext_len != 4) 171 goto discard_ext; 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; 178 else 179 s->transparent_color_index = -1; 180 s->gce_disposal = (gce_flags >> 2) & 0x7; 181#ifdef DEBUG 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); 185#endif 186 ext_len = bytestream_get_byte(&s->bytestream); 187 break; 188 } 189 190 /* NOTE: many extension blocks can come after */ 191 discard_ext: 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); 196#ifdef DEBUG 197 dprintf(s->avctx, "gif: ext_len1=%d\n", ext_len); 198#endif 199 } 200 return 0; 201} 202 203static int gif_read_header1(GifState *s) 204{ 205 uint8_t sig[6]; 206 int v, n; 207 int has_global_palette; 208 209 if (s->bytestream_end < s->bytestream + 13) 210 return -1; 211 212 /* 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) 216 return -1; 217 218 /* 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"); 225 return -1; 226 } 227 228 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 */ 234#ifdef DEBUG 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, 237 has_global_palette); 238#endif 239 if (has_global_palette) { 240 n = 1 << s->bits_per_pixel; 241 if (s->bytestream_end < s->bytestream + n * 3) 242 return -1; 243 bytestream_get_buffer(&s->bytestream, s->global_palette, n * 3); 244 } 245 return 0; 246} 247 248static int gif_parse_next_image(GifState *s) 249{ 250 while (s->bytestream < s->bytestream_end) { 251 int code = bytestream_get_byte(&s->bytestream); 252#ifdef DEBUG 253 dprintf(s->avctx, "gif: code=%02x '%c'\n", code, code); 254#endif 255 switch (code) { 256 case ',': 257 return gif_read_image(s); 258 case '!': 259 if (gif_read_extension(s) < 0) 260 return -1; 261 break; 262 case ';': 263 /* end of image */ 264 default: 265 /* error or erroneous EOF */ 266 return -1; 267 } 268 } 269 return -1; 270} 271 272static av_cold int gif_decode_init(AVCodecContext *avctx) 273{ 274 GifState *s = avctx->priv_data; 275 276 s->avctx = avctx; 277 278 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); 282 return 0; 283} 284 285static int gif_decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt) 286{ 287 const uint8_t *buf = avpkt->data; 288 int buf_size = avpkt->size; 289 GifState *s = avctx->priv_data; 290 AVFrame *picture = data; 291 int ret; 292 293 s->bytestream = buf; 294 s->bytestream_end = buf + buf_size; 295 if (gif_read_header1(s) < 0) 296 return -1; 297 298 avctx->pix_fmt = PIX_FMT_PAL8; 299 if (avcodec_check_dimensions(avctx, s->screen_width, s->screen_height)) 300 return -1; 301 avcodec_set_dimensions(avctx, s->screen_width, s->screen_height); 302 303 if (s->picture.data[0]) 304 avctx->release_buffer(avctx, &s->picture); 305 if (avctx->get_buffer(avctx, &s->picture) < 0) { 306 av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n"); 307 return -1; 308 } 309 s->image_palette = (uint32_t *)s->picture.data[1]; 310 ret = gif_parse_next_image(s); 311 if (ret < 0) 312 return ret; 313 314 *picture = s->picture; 315 *data_size = sizeof(AVPicture); 316 return s->bytestream - buf; 317} 318 319static av_cold int gif_decode_close(AVCodecContext *avctx) 320{ 321 GifState *s = avctx->priv_data; 322 323 ff_lzw_decode_close(&s->lzw); 324 if(s->picture.data[0]) 325 avctx->release_buffer(avctx, &s->picture); 326 return 0; 327} 328 329AVCodec gif_decoder = { 330 "gif", 331 AVMEDIA_TYPE_VIDEO, 332 CODEC_ID_GIF, 333 sizeof(GifState), 334 gif_decode_init, 335 NULL, 336 gif_decode_close, 337 gif_decode_frame, 338 CODEC_CAP_DR1, 339 .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"), 340}; 341