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     uint8_t *bytestream;
  51     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) |
 100             (spal[0] << 16) | (spal[1] << 8) | (spal[2]);
 101         spal += 3;
 102     }
 103     for(; i < 256; i++)
 104         s->image_palette[i] = (0xff << 24);
 105     /* handle transparency */
 106     if (s->transparent_color_index >= 0)
 107         s->image_palette[s->transparent_color_index] = 0;
 108
 109     /* now get the image data */
 110     code_size = bytestream_get_byte(&s->bytestream);
 111     ff_lzw_decode_init(s->lzw, code_size, s->bytestream,
 112                        s->bytestream_end - s->bytestream, FF_LZW_GIF);
 113
 114     /* read all the image */
 115     linesize = s->picture.linesize[0];
 116     ptr1 = s->picture.data[0] + top * linesize + left;
 117     ptr = ptr1;
 118     pass = 0;
 119     y1 = 0;
 120     for (y = 0; y < height; y++) {
 121         ff_lzw_decode(s->lzw, ptr, width);
 122         if (is_interleaved) {
 123             switch(pass) {
 124             default:
 125             case 0:
 126             case 1:
 127                 y1 += 8;
 128                 ptr += linesize * 8;
 129                 if (y1 >= height) {
 130                     y1 = 4;
 131                     if (pass == 0)
 132                         ptr = ptr1 + linesize * 4;
 133                     else
 134                         ptr = ptr1 + linesize * 2;
 135                     pass++;
 136                 }
 137                 break;
 138             case 2:
 139                 y1 += 4;
 140                 ptr += linesize * 4;
 141                 if (y1 >= height) {
 142                     y1 = 1;
 143                     ptr = ptr1 + linesize;
 144                     pass++;
 145                 }
 146                 break;
 147             case 3:
 148                 y1 += 2;
 149                 ptr += linesize * 2;
 150                 break;
 151             }
 152         } else {
 153             ptr += linesize;
 154         }
 155     }
 156     /* read the garbage data until end marker is found */
 157     ff_lzw_decode_tail(s->lzw);
 158     s->bytestream = ff_lzw_cur_ptr(s->lzw);
 159     return 0;
 160 }
 161
 162 static int gif_read_extension(GifState *s)
 163 {
 164     int ext_code, ext_len, i, gce_flags, gce_transparent_index;
 165
 166     /* extension */
 167     ext_code = bytestream_get_byte(&s->bytestream);
 168     ext_len = bytestream_get_byte(&s->bytestream);
 169 #ifdef DEBUG
 170     dprintf(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
 171 #endif
 172     switch(ext_code) {
 173     case 0xf9:
 174         if (ext_len != 4)
 175             goto discard_ext;
 176         s->transparent_color_index = -1;
 177         gce_flags = bytestream_get_byte(&s->bytestream);
 178         s->gce_delay = bytestream_get_le16(&s->bytestream);
 179         gce_transparent_index = bytestream_get_byte(&s->bytestream);
 180         if (gce_flags & 0x01)
 181             s->transparent_color_index = gce_transparent_index;
 182         else
 183             s->transparent_color_index = -1;
 184         s->gce_disposal = (gce_flags >> 2) & 0x7;
 185 #ifdef DEBUG
 186         dprintf(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
 187                gce_flags, s->gce_delay,
 188                s->transparent_color_index, s->gce_disposal);
 189 #endif
 190         ext_len = bytestream_get_byte(&s->bytestream);
 191         break;
 192     }
 193
 194     /* NOTE: many extension blocks can come after */
 195  discard_ext:
 196     while (ext_len != 0) {
 197         for (i = 0; i < ext_len; i++)
 198             bytestream_get_byte(&s->bytestream);
 199         ext_len = bytestream_get_byte(&s->bytestream);
 200 #ifdef DEBUG
 201         dprintf(s->avctx, "gif: ext_len1=%d\n", ext_len);
 202 #endif
 203     }
 204     return 0;
 205 }
 206
 207 static int gif_read_header1(GifState *s)
 208 {
 209     uint8_t sig[6];
 210     int v, n;
 211     int has_global_palette;
 212
 213     if (s->bytestream_end < s->bytestream + 13)
 214         return -1;
 215
 216     /* read gif signature */
 217     bytestream_get_buffer(&s->bytestream, sig, 6);
 218     if (memcmp(sig, gif87a_sig, 6) != 0 &&
 219         memcmp(sig, gif89a_sig, 6) != 0)
 220         return -1;
 221
 222     /* read screen header */
 223     s->transparent_color_index = -1;
 224     s->screen_width = bytestream_get_le16(&s->bytestream);
 225     s->screen_height = bytestream_get_le16(&s->bytestream);
 226     if(   (unsigned)s->screen_width  > 32767
 227        || (unsigned)s->screen_height > 32767){
 228         av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
 229         return -1;
 230     }
 231
 232     v = bytestream_get_byte(&s->bytestream);
 233     s->color_resolution = ((v & 0x70) >> 4) + 1;
 234     has_global_palette = (v & 0x80);
 235     s->bits_per_pixel = (v & 0x07) + 1;
 236     s->background_color_index = bytestream_get_byte(&s->bytestream);
 237     bytestream_get_byte(&s->bytestream);                /* ignored */
 238 #ifdef DEBUG
 239     dprintf(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
 240            s->screen_width, s->screen_height, s->bits_per_pixel,
 241            has_global_palette);
 242 #endif
 243     if (has_global_palette) {
 244         n = 1 << s->bits_per_pixel;
 245         if (s->bytestream_end < s->bytestream + n * 3)
 246             return -1;
 247         bytestream_get_buffer(&s->bytestream, s->global_palette, n * 3);
 248     }
 249     return 0;
 250 }
 251
 252 static int gif_parse_next_image(GifState *s)
 253 {
 254     while (s->bytestream < s->bytestream_end) {
 255         int code = bytestream_get_byte(&s->bytestream);
 256 #ifdef DEBUG
 257         dprintf(s->avctx, "gif: code=%02x '%c'\n", code, code);
 258 #endif
 259         switch (code) {
 260         case ',':
 261             return gif_read_image(s);
 262         case '!':
 263             if (gif_read_extension(s) < 0)
 264                 return -1;
 265             break;
 266         case ';':
 267             /* end of image */
 268         default:
 269             /* error or erroneous EOF */
 270             return -1;
 271         }
 272     }
 273     return -1;
 274 }
 275
 276 static int gif_decode_init(AVCodecContext *avctx)
 277 {
 278     GifState *s = avctx->priv_data;
 279
 280     s->avctx = avctx;
 281
 282     avcodec_get_frame_defaults(&s->picture);
 283     avctx->coded_frame= &s->picture;
 284     s->picture.data[0] = NULL;
 285     ff_lzw_decode_open(&s->lzw);
 286     return 0;
 287 }
 288
 289 static int gif_decode_frame(AVCodecContext *avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
 290 {
 291     GifState *s = avctx->priv_data;
 292     AVFrame *picture = data;
 293     int ret;
 294
 295     s->bytestream = buf;
 296     s->bytestream_end = buf + buf_size;
 297     if (gif_read_header1(s) < 0)
 298         return -1;
 299
 300     avctx->pix_fmt = PIX_FMT_PAL8;
 301     if (avcodec_check_dimensions(avctx, s->screen_width, s->screen_height))
 302         return -1;
 303     avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);
 304
 305     if (s->picture.data[0])
 306         avctx->release_buffer(avctx, &s->picture);
 307     if (avctx->get_buffer(avctx, &s->picture) < 0) {
 308         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
 309         return -1;
 310     }
 311     s->image_palette = (uint32_t *)s->picture.data[1];
 312     ret = gif_parse_next_image(s);
 313     if (ret < 0)
 314         return ret;
 315
 316     *picture = s->picture;
 317     *data_size = sizeof(AVPicture);
 318     return s->bytestream - buf;
 319 }
 320
 321 static int gif_decode_close(AVCodecContext *avctx)
 322 {
 323     GifState *s = avctx->priv_data;
 324
 325     ff_lzw_decode_close(&s->lzw);
 326     if(s->picture.data[0])
 327         avctx->release_buffer(avctx, &s->picture);
 328     return 0;
 329 }
 330
 331 AVCodec gif_decoder = {
 332     "gif",
 333     CODEC_TYPE_VIDEO,
 334     CODEC_ID_GIF,
 335     sizeof(GifState),
 336     gif_decode_init,
 337     NULL,
 338     gif_decode_close,
 339     gif_decode_frame,
 340 };