FFmpeg: libavcodec/gifdec.c Source File

00001 /*
00002  * GIF decoder
00003  * Copyright (c) 2003 Fabrice Bellard
00004  * Copyright (c) 2006 Baptiste Coudurier
00005  *
00006  * This file is part of FFmpeg.
00007  *
00008  * FFmpeg is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * FFmpeg is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with FFmpeg; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00023 //#define DEBUG
00024 
00025 #include "libavutil/imgutils.h"
00026 #include "avcodec.h"
00027 #include "bytestream.h"
00028 #include "lzw.h"
00029 
00030 #define GCE_DISPOSAL_NONE       0
00031 #define GCE_DISPOSAL_INPLACE    1
00032 #define GCE_DISPOSAL_BACKGROUND 2
00033 #define GCE_DISPOSAL_RESTORE    3
00034 
00035 typedef struct GifState {
00036     AVFrame picture;
00037     int screen_width;
00038     int screen_height;
00039     int bits_per_pixel;
00040     int background_color_index;
00041     int transparent_color_index;
00042     int color_resolution;
00043     uint32_t *image_palette;
00044 
00045     /* after the frame is displayed, the disposal method is used */
00046     int gce_disposal;
00047     /* delay during which the frame is shown */
00048     int gce_delay;
00049 
00050     /* LZW compatible decoder */
00051     const uint8_t *bytestream;
00052     const uint8_t *bytestream_end;
00053     LZWState *lzw;
00054 
00055     /* aux buffers */
00056     uint8_t global_palette[256 * 3];
00057     uint8_t local_palette[256 * 3];
00058 
00059   AVCodecContext* avctx;
00060 } GifState;
00061 
00062 static const uint8_t gif87a_sig[6] = "GIF87a";
00063 static const uint8_t gif89a_sig[6] = "GIF89a";
00064 
00065 static int gif_read_image(GifState *s)
00066 {
00067     int left, top, width, height, bits_per_pixel, code_size, flags;
00068     int is_interleaved, has_local_palette, y, pass, y1, linesize, n, i;
00069     uint8_t *ptr, *spal, *palette, *ptr1;
00070 
00071     left = bytestream_get_le16(&s->bytestream);
00072     top = bytestream_get_le16(&s->bytestream);
00073     width = bytestream_get_le16(&s->bytestream);
00074     height = bytestream_get_le16(&s->bytestream);
00075     flags = bytestream_get_byte(&s->bytestream);
00076     is_interleaved = flags & 0x40;
00077     has_local_palette = flags & 0x80;
00078     bits_per_pixel = (flags & 0x07) + 1;
00079 
00080     av_dlog(s->avctx, "gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
00081 
00082     if (has_local_palette) {
00083         bytestream_get_buffer(&s->bytestream, s->local_palette, 3 * (1 << bits_per_pixel));
00084         palette = s->local_palette;
00085     } else {
00086         palette = s->global_palette;
00087         bits_per_pixel = s->bits_per_pixel;
00088     }
00089 
00090     /* verify that all the image is inside the screen dimensions */
00091     if (left + width > s->screen_width ||
00092         top + height > s->screen_height)
00093         return AVERROR(EINVAL);
00094 
00095     /* build the palette */
00096     n = (1 << bits_per_pixel);
00097     spal = palette;
00098     for(i = 0; i < n; i++) {
00099         s->image_palette[i] = (0xff << 24) | AV_RB24(spal);
00100         spal += 3;
00101     }
00102     for(; i < 256; i++)
00103         s->image_palette[i] = (0xff << 24);
00104     /* handle transparency */
00105     if (s->transparent_color_index >= 0)
00106         s->image_palette[s->transparent_color_index] = 0;
00107 
00108     /* now get the image data */
00109     code_size = bytestream_get_byte(&s->bytestream);
00110     ff_lzw_decode_init(s->lzw, code_size, s->bytestream,
00111                        s->bytestream_end - s->bytestream, FF_LZW_GIF);
00112 
00113     /* read all the image */
00114     linesize = s->picture.linesize[0];
00115     ptr1 = s->picture.data[0] + top * linesize + left;
00116     ptr = ptr1;
00117     pass = 0;
00118     y1 = 0;
00119     for (y = 0; y < height; y++) {
00120         ff_lzw_decode(s->lzw, ptr, width);
00121         if (is_interleaved) {
00122             switch(pass) {
00123             default:
00124             case 0:
00125             case 1:
00126                 y1 += 8;
00127                 ptr += linesize * 8;
00128                 if (y1 >= height) {
00129                     y1 = pass ? 2 : 4;
00130                     ptr = ptr1 + linesize * y1;
00131                     pass++;
00132                 }
00133                 break;
00134             case 2:
00135                 y1 += 4;
00136                 ptr += linesize * 4;
00137                 if (y1 >= height) {
00138                     y1 = 1;
00139                     ptr = ptr1 + linesize;
00140                     pass++;
00141                 }
00142                 break;
00143             case 3:
00144                 y1 += 2;
00145                 ptr += linesize * 2;
00146                 break;
00147             }
00148         } else {
00149             ptr += linesize;
00150         }
00151     }
00152     /* read the garbage data until end marker is found */
00153     ff_lzw_decode_tail(s->lzw);
00154     s->bytestream = ff_lzw_cur_ptr(s->lzw);
00155     return 0;
00156 }
00157 
00158 static int gif_read_extension(GifState *s)
00159 {
00160     int ext_code, ext_len, i, gce_flags, gce_transparent_index;
00161 
00162     /* extension */
00163     ext_code = bytestream_get_byte(&s->bytestream);
00164     ext_len = bytestream_get_byte(&s->bytestream);
00165 
00166     av_dlog(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
00167 
00168     switch(ext_code) {
00169     case 0xf9:
00170         if (ext_len != 4)
00171             goto discard_ext;
00172         s->transparent_color_index = -1;
00173         gce_flags = bytestream_get_byte(&s->bytestream);
00174         s->gce_delay = bytestream_get_le16(&s->bytestream);
00175         gce_transparent_index = bytestream_get_byte(&s->bytestream);
00176         if (gce_flags & 0x01)
00177             s->transparent_color_index = gce_transparent_index;
00178         else
00179             s->transparent_color_index = -1;
00180         s->gce_disposal = (gce_flags >> 2) & 0x7;
00181 
00182         av_dlog(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
00183                gce_flags, s->gce_delay,
00184                s->transparent_color_index, s->gce_disposal);
00185 
00186         ext_len = bytestream_get_byte(&s->bytestream);
00187         break;
00188     }
00189 
00190     /* NOTE: many extension blocks can come after */
00191  discard_ext:
00192     while (ext_len != 0) {
00193         for (i = 0; i < ext_len; i++)
00194             bytestream_get_byte(&s->bytestream);
00195         ext_len = bytestream_get_byte(&s->bytestream);
00196 
00197         av_dlog(s->avctx, "gif: ext_len1=%d\n", ext_len);
00198     }
00199     return 0;
00200 }
00201 
00202 static int gif_read_header1(GifState *s)
00203 {
00204     uint8_t sig[6];
00205     int v, n;
00206     int has_global_palette;
00207 
00208     if (s->bytestream_end < s->bytestream + 13)
00209         return -1;
00210 
00211     /* read gif signature */
00212     bytestream_get_buffer(&s->bytestream, sig, 6);
00213     if (memcmp(sig, gif87a_sig, 6) != 0 &&
00214         memcmp(sig, gif89a_sig, 6) != 0)
00215         return -1;
00216 
00217     /* read screen header */
00218     s->transparent_color_index = -1;
00219     s->screen_width = bytestream_get_le16(&s->bytestream);
00220     s->screen_height = bytestream_get_le16(&s->bytestream);
00221     if(   (unsigned)s->screen_width  > 32767
00222        || (unsigned)s->screen_height > 32767){
00223         av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
00224         return -1;
00225     }
00226 
00227     v = bytestream_get_byte(&s->bytestream);
00228     s->color_resolution = ((v & 0x70) >> 4) + 1;
00229     has_global_palette = (v & 0x80);
00230     s->bits_per_pixel = (v & 0x07) + 1;
00231     s->background_color_index = bytestream_get_byte(&s->bytestream);
00232     bytestream_get_byte(&s->bytestream);                /* ignored */
00233 
00234     av_dlog(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
00235            s->screen_width, s->screen_height, s->bits_per_pixel,
00236            has_global_palette);
00237 
00238     if (has_global_palette) {
00239         n = 1 << s->bits_per_pixel;
00240         if (s->bytestream_end < s->bytestream + n * 3)
00241             return -1;
00242         bytestream_get_buffer(&s->bytestream, s->global_palette, n * 3);
00243     }
00244     return 0;
00245 }
00246 
00247 static int gif_parse_next_image(GifState *s)
00248 {
00249     while (s->bytestream < s->bytestream_end) {
00250         int code = bytestream_get_byte(&s->bytestream);
00251 
00252         av_dlog(s->avctx, "gif: code=%02x '%c'\n", code, code);
00253 
00254         switch (code) {
00255         case ',':
00256             return gif_read_image(s);
00257         case '!':
00258             if (gif_read_extension(s) < 0)
00259                 return -1;
00260             break;
00261         case ';':
00262             /* end of image */
00263         default:
00264             /* error or erroneous EOF */
00265             return -1;
00266         }
00267     }
00268     return -1;
00269 }
00270 
00271 static av_cold int gif_decode_init(AVCodecContext *avctx)
00272 {
00273     GifState *s = avctx->priv_data;
00274 
00275     s->avctx = avctx;
00276 
00277     avcodec_get_frame_defaults(&s->picture);
00278     avctx->coded_frame= &s->picture;
00279     s->picture.data[0] = NULL;
00280     ff_lzw_decode_open(&s->lzw);
00281     return 0;
00282 }
00283 
00284 static int gif_decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)
00285 {
00286     const uint8_t *buf = avpkt->data;
00287     int buf_size = avpkt->size;
00288     GifState *s = avctx->priv_data;
00289     AVFrame *picture = data;
00290     int ret;
00291 
00292     s->bytestream = buf;
00293     s->bytestream_end = buf + buf_size;
00294     if (gif_read_header1(s) < 0)
00295         return -1;
00296 
00297     avctx->pix_fmt = PIX_FMT_PAL8;
00298     if (av_image_check_size(s->screen_width, s->screen_height, 0, avctx))
00299         return -1;
00300     avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);
00301 
00302     if (s->picture.data[0])
00303         avctx->release_buffer(avctx, &s->picture);
00304     if (avctx->get_buffer(avctx, &s->picture) < 0) {
00305         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
00306         return -1;
00307     }
00308     s->image_palette = (uint32_t *)s->picture.data[1];
00309     ret = gif_parse_next_image(s);
00310     if (ret < 0)
00311         return ret;
00312 
00313     *picture = s->picture;
00314     *data_size = sizeof(AVPicture);
00315     return s->bytestream - buf;
00316 }
00317 
00318 static av_cold int gif_decode_close(AVCodecContext *avctx)
00319 {
00320     GifState *s = avctx->priv_data;
00321 
00322     ff_lzw_decode_close(&s->lzw);
00323     if(s->picture.data[0])
00324         avctx->release_buffer(avctx, &s->picture);
00325     return 0;
00326 }
00327 
00328 AVCodec ff_gif_decoder = {
00329     "gif",
00330     AVMEDIA_TYPE_VIDEO,
00331     CODEC_ID_GIF,
00332     sizeof(GifState),
00333     gif_decode_init,
00334     NULL,
00335     gif_decode_close,
00336     gif_decode_frame,
00337     CODEC_CAP_DR1,
00338     .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
00339 };