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 Libav.
   7  *
   8  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "libavutil/imgutils.h"
  24 #include "avcodec.h"
  25 #include "bytestream.h"
  26 #include "internal.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     int screen_width;
  36     int screen_height;
  37     int bits_per_pixel;
  38     int background_color_index;
  39     int transparent_color_index;
  40     int color_resolution;
  41     uint32_t *image_palette;
  42
  43     /* after the frame is displayed, the disposal method is used */
  44     int gce_disposal;
  45     /* delay during which the frame is shown */
  46     int gce_delay;
  47
  48     /* LZW compatible decoder */
  49     GetByteContext gb;
  50     LZWState *lzw;
  51
  52     /* aux buffers */
  53     uint8_t global_palette[256 * 3];
  54     uint8_t local_palette[256 * 3];
  55
  56   AVCodecContext* avctx;
  57 } GifState;
  58
  59 static const uint8_t gif87a_sig[6] = "GIF87a";
  60 static const uint8_t gif89a_sig[6] = "GIF89a";
  61
  62 static int gif_read_image(GifState *s, AVFrame *frame)
  63 {
  64     int left, top, width, height, bits_per_pixel, code_size, flags;
  65     int is_interleaved, has_local_palette, y, pass, y1, linesize, n, i;
  66     uint8_t *ptr, *spal, *palette, *ptr1;
  67
  68     left   = bytestream2_get_le16(&s->gb);
  69     top    = bytestream2_get_le16(&s->gb);
  70     width  = bytestream2_get_le16(&s->gb);
  71     height = bytestream2_get_le16(&s->gb);
  72     flags  = bytestream2_get_byte(&s->gb);
  73     is_interleaved = flags & 0x40;
  74     has_local_palette = flags & 0x80;
  75     bits_per_pixel = (flags & 0x07) + 1;
  76
  77     ff_dlog(s->avctx, "gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
  78
  79     if (has_local_palette) {
  80         bytestream2_get_buffer(&s->gb, s->local_palette, 3 * (1 << bits_per_pixel));
  81         palette = s->local_palette;
  82     } else {
  83         palette = s->global_palette;
  84         bits_per_pixel = s->bits_per_pixel;
  85     }
  86
  87     /* verify that all the image is inside the screen dimensions */
  88     if (left + width > s->screen_width ||
  89         top + height > s->screen_height ||
  90         !width || !height) {
  91         av_log(s->avctx, AV_LOG_ERROR, "Invalid image dimensions.\n");
  92         return AVERROR_INVALIDDATA;
  93     }
  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] = (0xffu << 24) | AV_RB24(spal);
 100         spal += 3;
 101     }
 102     for(; i < 256; i++)
 103         s->image_palette[i] = (0xffu << 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 = bytestream2_get_byte(&s->gb);
 110     ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
 111                        bytestream2_get_bytes_left(&s->gb), FF_LZW_GIF);
 112
 113     /* read all the image */
 114     linesize = frame->linesize[0];
 115     ptr1 = frame->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                 break;
 129             case 2:
 130                 y1 += 4;
 131                 ptr += linesize * 4;
 132                 break;
 133             case 3:
 134                 y1 += 2;
 135                 ptr += linesize * 2;
 136                 break;
 137             }
 138             while (y1 >= height) {
 139                 y1  = 4 >> pass;
 140                 ptr = ptr1 + linesize * y1;
 141                 pass++;
 142             }
 143         } else {
 144             ptr += linesize;
 145         }
 146     }
 147     /* read the garbage data until end marker is found */
 148     ff_lzw_decode_tail(s->lzw);
 149
 150     bytestream2_skip(&s->gb, ff_lzw_size_read(s->lzw));
 151     return 0;
 152 }
 153
 154 static int gif_read_extension(GifState *s)
 155 {
 156     int ext_code, ext_len, i, gce_flags, gce_transparent_index;
 157
 158     /* extension */
 159     ext_code = bytestream2_get_byte(&s->gb);
 160     ext_len  = bytestream2_get_byte(&s->gb);
 161
 162     ff_dlog(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
 163
 164     switch(ext_code) {
 165     case 0xf9:
 166         if (ext_len != 4)
 167             goto discard_ext;
 168         s->transparent_color_index = -1;
 169         gce_flags    = bytestream2_get_byte(&s->gb);
 170         s->gce_delay = bytestream2_get_le16(&s->gb);
 171         gce_transparent_index = bytestream2_get_byte(&s->gb);
 172         if (gce_flags & 0x01)
 173             s->transparent_color_index = gce_transparent_index;
 174         else
 175             s->transparent_color_index = -1;
 176         s->gce_disposal = (gce_flags >> 2) & 0x7;
 177
 178         ff_dlog(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
 179                gce_flags, s->gce_delay,
 180                s->transparent_color_index, s->gce_disposal);
 181
 182         ext_len = bytestream2_get_byte(&s->gb);
 183         break;
 184     }
 185
 186     /* NOTE: many extension blocks can come after */
 187  discard_ext:
 188     while (ext_len != 0) {
 189         for (i = 0; i < ext_len; i++)
 190             bytestream2_get_byte(&s->gb);
 191         ext_len = bytestream2_get_byte(&s->gb);
 192
 193         ff_dlog(s->avctx, "gif: ext_len1=%d\n", ext_len);
 194     }
 195     return 0;
 196 }
 197
 198 static int gif_read_header1(GifState *s)
 199 {
 200     uint8_t sig[6];
 201     int v, n;
 202     int has_global_palette;
 203
 204     if (bytestream2_get_bytes_left(&s->gb) < 13)
 205         return AVERROR_INVALIDDATA;
 206
 207     /* read gif signature */
 208     bytestream2_get_buffer(&s->gb, sig, 6);
 209     if (memcmp(sig, gif87a_sig, 6) != 0 &&
 210         memcmp(sig, gif89a_sig, 6) != 0)
 211         return AVERROR_INVALIDDATA;
 212
 213     /* read screen header */
 214     s->transparent_color_index = -1;
 215     s->screen_width  = bytestream2_get_le16(&s->gb);
 216     s->screen_height = bytestream2_get_le16(&s->gb);
 217     if(   (unsigned)s->screen_width  > 32767
 218        || (unsigned)s->screen_height > 32767){
 219         av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
 220         return AVERROR_INVALIDDATA;
 221     }
 222
 223     v = bytestream2_get_byte(&s->gb);
 224     s->color_resolution = ((v & 0x70) >> 4) + 1;
 225     has_global_palette = (v & 0x80);
 226     s->bits_per_pixel = (v & 0x07) + 1;
 227     s->background_color_index = bytestream2_get_byte(&s->gb);
 228     bytestream2_get_byte(&s->gb);                /* ignored */
 229
 230     ff_dlog(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
 231            s->screen_width, s->screen_height, s->bits_per_pixel,
 232            has_global_palette);
 233
 234     if (has_global_palette) {
 235         n = 1 << s->bits_per_pixel;
 236         if (bytestream2_get_bytes_left(&s->gb) < n * 3)
 237             return AVERROR_INVALIDDATA;
 238         bytestream2_get_buffer(&s->gb, s->global_palette, n * 3);
 239     }
 240     return 0;
 241 }
 242
 243 static int gif_parse_next_image(GifState *s, AVFrame *frame)
 244 {
 245     while (bytestream2_get_bytes_left(&s->gb) > 0) {
 246         int code = bytestream2_get_byte(&s->gb);
 247         int ret;
 248
 249         ff_dlog(s->avctx, "gif: code=%02x '%c'\n", code, code);
 250
 251         switch (code) {
 252         case ',':
 253             return gif_read_image(s, frame);
 254         case '!':
 255             if ((ret = gif_read_extension(s)) < 0)
 256                 return ret;
 257             break;
 258         case ';':
 259             /* end of image */
 260         default:
 261             /* error or erroneous EOF */
 262             return AVERROR_INVALIDDATA;
 263         }
 264     }
 265     return AVERROR_INVALIDDATA;
 266 }
 267
 268 static av_cold int gif_decode_init(AVCodecContext *avctx)
 269 {
 270     GifState *s = avctx->priv_data;
 271
 272     s->avctx = avctx;
 273
 274     ff_lzw_decode_open(&s->lzw);
 275     return 0;
 276 }
 277
 278 static int gif_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
 279                             AVPacket *avpkt)
 280 {
 281     const uint8_t *buf = avpkt->data;
 282     int buf_size = avpkt->size;
 283     GifState *s = avctx->priv_data;
 284     AVFrame *picture = data;
 285     int ret;
 286
 287     bytestream2_init(&s->gb, buf, buf_size);
 288     if ((ret = gif_read_header1(s)) < 0)
 289         return ret;
 290
 291     avctx->pix_fmt = AV_PIX_FMT_PAL8;
 292
 293     if ((ret = ff_set_dimensions(avctx, s->screen_width, s->screen_height)) < 0)
 294         return ret;
 295
 296     if ((ret = ff_get_buffer(avctx, picture, 0)) < 0) {
 297         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
 298         return ret;
 299     }
 300     s->image_palette = (uint32_t *)picture->data[1];
 301     ret = gif_parse_next_image(s, picture);
 302     if (ret < 0)
 303         return ret;
 304
 305     *got_frame = 1;
 306     return bytestream2_tell(&s->gb);
 307 }
 308
 309 static av_cold int gif_decode_close(AVCodecContext *avctx)
 310 {
 311     GifState *s = avctx->priv_data;
 312
 313     ff_lzw_decode_close(&s->lzw);
 314     return 0;
 315 }
 316
 317 AVCodec ff_gif_decoder = {
 318     .name           = "gif",
 319     .long_name      = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
 320     .type           = AVMEDIA_TYPE_VIDEO,
 321     .id             = AV_CODEC_ID_GIF,
 322     .priv_data_size = sizeof(GifState),
 323     .init           = gif_decode_init,
 324     .close          = gif_decode_close,
 325     .decode         = gif_decode_frame,
 326     .capabilities   = AV_CODEC_CAP_DR1,
 327 };