libavcodec/gifdec.c

   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
  34 typedef 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
  61 static const uint8_t gif87a_sig[6] = "GIF87a";
  62 static const uint8_t gif89a_sig[6] = "GIF89a";
  63
  64 static 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
 158 static 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
 203 static 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
 248 static 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
 272 static 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
 285 static int gif_decode_frame(AVCodecContext *avctx, void *data, int *data_size, const uint8_t *buf, int buf_size)
 286 {
 287     GifState *s = avctx->priv_data;
 288     AVFrame *picture = data;
 289     int ret;
 290
 291     s->bytestream = buf;
 292     s->bytestream_end = buf + buf_size;
 293     if (gif_read_header1(s) < 0)
 294         return -1;
 295
 296     avctx->pix_fmt = PIX_FMT_PAL8;
 297     if (avcodec_check_dimensions(avctx, s->screen_width, s->screen_height))
 298         return -1;
 299     avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);
 300
 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");
 305         return -1;
 306     }
 307     s->image_palette = (uint32_t *)s->picture.data[1];
 308     ret = gif_parse_next_image(s);
 309     if (ret < 0)
 310         return ret;
 311
 312     *picture = s->picture;
 313     *data_size = sizeof(AVPicture);
 314     return s->bytestream - buf;
 315 }
 316
 317 static av_cold int gif_decode_close(AVCodecContext *avctx)
 318 {
 319     GifState *s = avctx->priv_data;
 320
 321     ff_lzw_decode_close(&s->lzw);
 322     if(s->picture.data[0])
 323         avctx->release_buffer(avctx, &s->picture);
 324     return 0;
 325 }
 326
 327 AVCodec gif_decoder = {
 328     "gif",
 329     CODEC_TYPE_VIDEO,
 330     CODEC_ID_GIF,
 331     sizeof(GifState),
 332     gif_decode_init,
 333     NULL,
 334     gif_decode_close,
 335     gif_decode_frame,
 336     .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
 337 };