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 "libavcore/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 #ifdef DEBUG
00080     dprintf(s->avctx, "gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
00081 #endif
00082 
00083     if (has_local_palette) {
00084         bytestream_get_buffer(&s->bytestream, s->local_palette, 3 * (1 << bits_per_pixel));
00085         palette = s->local_palette;
00086     } else {
00087         palette = s->global_palette;
00088         bits_per_pixel = s->bits_per_pixel;
00089     }
00090 
00091     /* verify that all the image is inside the screen dimensions */
00092     if (left + width > s->screen_width ||
00093         top + height > s->screen_height)
00094         return AVERROR(EINVAL);
00095 
00096     /* build the palette */
00097     n = (1 << bits_per_pixel);
00098     spal = palette;
00099     for(i = 0; i < n; i++) {
00100         s->image_palette[i] = (0xff << 24) | AV_RB24(spal);
00101         spal += 3;
00102     }
00103     for(; i < 256; i++)
00104         s->image_palette[i] = (0xff << 24);
00105     /* handle transparency */
00106     if (s->transparent_color_index >= 0)
00107         s->image_palette[s->transparent_color_index] = 0;
00108 
00109     /* now get the image data */
00110     code_size = bytestream_get_byte(&s->bytestream);
00111     ff_lzw_decode_init(s->lzw, code_size, s->bytestream,
00112                        s->bytestream_end - s->bytestream, FF_LZW_GIF);
00113 
00114     /* read all the image */
00115     linesize = s->picture.linesize[0];
00116     ptr1 = s->picture.data[0] + top * linesize + left;
00117     ptr = ptr1;
00118     pass = 0;
00119     y1 = 0;
00120     for (y = 0; y < height; y++) {
00121         ff_lzw_decode(s->lzw, ptr, width);
00122         if (is_interleaved) {
00123             switch(pass) {
00124             default:
00125             case 0:
00126             case 1:
00127                 y1 += 8;
00128                 ptr += linesize * 8;
00129                 if (y1 >= height) {
00130                     y1 = pass ? 2 : 4;
00131                     ptr = ptr1 + linesize * y1;
00132                     pass++;
00133                 }
00134                 break;
00135             case 2:
00136                 y1 += 4;
00137                 ptr += linesize * 4;
00138                 if (y1 >= height) {
00139                     y1 = 1;
00140                     ptr = ptr1 + linesize;
00141                     pass++;
00142                 }
00143                 break;
00144             case 3:
00145                 y1 += 2;
00146                 ptr += linesize * 2;
00147                 break;
00148             }
00149         } else {
00150             ptr += linesize;
00151         }
00152     }
00153     /* read the garbage data until end marker is found */
00154     ff_lzw_decode_tail(s->lzw);
00155     s->bytestream = ff_lzw_cur_ptr(s->lzw);
00156     return 0;
00157 }
00158 
00159 static int gif_read_extension(GifState *s)
00160 {
00161     int ext_code, ext_len, i, gce_flags, gce_transparent_index;
00162 
00163     /* extension */
00164     ext_code = bytestream_get_byte(&s->bytestream);
00165     ext_len = bytestream_get_byte(&s->bytestream);
00166 #ifdef DEBUG
00167     dprintf(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
00168 #endif
00169     switch(ext_code) {
00170     case 0xf9:
00171         if (ext_len != 4)
00172             goto discard_ext;
00173         s->transparent_color_index = -1;
00174         gce_flags = bytestream_get_byte(&s->bytestream);
00175         s->gce_delay = bytestream_get_le16(&s->bytestream);
00176         gce_transparent_index = bytestream_get_byte(&s->bytestream);
00177         if (gce_flags & 0x01)
00178             s->transparent_color_index = gce_transparent_index;
00179         else
00180             s->transparent_color_index = -1;
00181         s->gce_disposal = (gce_flags >> 2) & 0x7;
00182 #ifdef DEBUG
00183         dprintf(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
00184                gce_flags, s->gce_delay,
00185                s->transparent_color_index, s->gce_disposal);
00186 #endif
00187         ext_len = bytestream_get_byte(&s->bytestream);
00188         break;
00189     }
00190 
00191     /* NOTE: many extension blocks can come after */
00192  discard_ext:
00193     while (ext_len != 0) {
00194         for (i = 0; i < ext_len; i++)
00195             bytestream_get_byte(&s->bytestream);
00196         ext_len = bytestream_get_byte(&s->bytestream);
00197 #ifdef DEBUG
00198         dprintf(s->avctx, "gif: ext_len1=%d\n", ext_len);
00199 #endif
00200     }
00201     return 0;
00202 }
00203 
00204 static int gif_read_header1(GifState *s)
00205 {
00206     uint8_t sig[6];
00207     int v, n;
00208     int has_global_palette;
00209 
00210     if (s->bytestream_end < s->bytestream + 13)
00211         return -1;
00212 
00213     /* read gif signature */
00214     bytestream_get_buffer(&s->bytestream, sig, 6);
00215     if (memcmp(sig, gif87a_sig, 6) != 0 &&
00216         memcmp(sig, gif89a_sig, 6) != 0)
00217         return -1;
00218 
00219     /* read screen header */
00220     s->transparent_color_index = -1;
00221     s->screen_width = bytestream_get_le16(&s->bytestream);
00222     s->screen_height = bytestream_get_le16(&s->bytestream);
00223     if(   (unsigned)s->screen_width  > 32767
00224        || (unsigned)s->screen_height > 32767){
00225         av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
00226         return -1;
00227     }
00228 
00229     v = bytestream_get_byte(&s->bytestream);
00230     s->color_resolution = ((v & 0x70) >> 4) + 1;
00231     has_global_palette = (v & 0x80);
00232     s->bits_per_pixel = (v & 0x07) + 1;
00233     s->background_color_index = bytestream_get_byte(&s->bytestream);
00234     bytestream_get_byte(&s->bytestream);                /* ignored */
00235 #ifdef DEBUG
00236     dprintf(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
00237            s->screen_width, s->screen_height, s->bits_per_pixel,
00238            has_global_palette);
00239 #endif
00240     if (has_global_palette) {
00241         n = 1 << s->bits_per_pixel;
00242         if (s->bytestream_end < s->bytestream + n * 3)
00243             return -1;
00244         bytestream_get_buffer(&s->bytestream, s->global_palette, n * 3);
00245     }
00246     return 0;
00247 }
00248 
00249 static int gif_parse_next_image(GifState *s)
00250 {
00251     while (s->bytestream < s->bytestream_end) {
00252         int code = bytestream_get_byte(&s->bytestream);
00253 #ifdef DEBUG
00254         dprintf(s->avctx, "gif: code=%02x '%c'\n", code, code);
00255 #endif
00256         switch (code) {
00257         case ',':
00258             return gif_read_image(s);
00259         case '!':
00260             if (gif_read_extension(s) < 0)
00261                 return -1;
00262             break;
00263         case ';':
00264             /* end of image */
00265         default:
00266             /* error or erroneous EOF */
00267             return -1;
00268         }
00269     }
00270     return -1;
00271 }
00272 
00273 static av_cold int gif_decode_init(AVCodecContext *avctx)
00274 {
00275     GifState *s = avctx->priv_data;
00276 
00277     s->avctx = avctx;
00278 
00279     avcodec_get_frame_defaults(&s->picture);
00280     avctx->coded_frame= &s->picture;
00281     s->picture.data[0] = NULL;
00282     ff_lzw_decode_open(&s->lzw);
00283     return 0;
00284 }
00285 
00286 static int gif_decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)
00287 {
00288     const uint8_t *buf = avpkt->data;
00289     int buf_size = avpkt->size;
00290     GifState *s = avctx->priv_data;
00291     AVFrame *picture = data;
00292     int ret;
00293 
00294     s->bytestream = buf;
00295     s->bytestream_end = buf + buf_size;
00296     if (gif_read_header1(s) < 0)
00297         return -1;
00298 
00299     avctx->pix_fmt = PIX_FMT_PAL8;
00300     if (av_image_check_size(s->screen_width, s->screen_height, 0, avctx))
00301         return -1;
00302     avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);
00303 
00304     if (s->picture.data[0])
00305         avctx->release_buffer(avctx, &s->picture);
00306     if (avctx->get_buffer(avctx, &s->picture) < 0) {
00307         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
00308         return -1;
00309     }
00310     s->image_palette = (uint32_t *)s->picture.data[1];
00311     ret = gif_parse_next_image(s);
00312     if (ret < 0)
00313         return ret;
00314 
00315     *picture = s->picture;
00316     *data_size = sizeof(AVPicture);
00317     return s->bytestream - buf;
00318 }
00319 
00320 static av_cold int gif_decode_close(AVCodecContext *avctx)
00321 {
00322     GifState *s = avctx->priv_data;
00323 
00324     ff_lzw_decode_close(&s->lzw);
00325     if(s->picture.data[0])
00326         avctx->release_buffer(avctx, &s->picture);
00327     return 0;
00328 }
00329 
00330 AVCodec gif_decoder = {
00331     "gif",
00332     AVMEDIA_TYPE_VIDEO,
00333     CODEC_ID_GIF,
00334     sizeof(GifState),
00335     gif_decode_init,
00336     NULL,
00337     gif_decode_close,
00338     gif_decode_frame,
00339     CODEC_CAP_DR1,
00340     .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
00341 };