Filters/FilterGif.cs

   1 //
   2 // FilterGif.cs
   3 //
   4 // Copyright (C) 2006 Alexander Macdonald <alex@alexmac.cc>
   5 //
   6
   7 //
   8 // Permission is hereby granted, free of charge, to any person obtaining a
   9 // copy of this software and associated documentation files (the "Software"),
  10 // to deal in the Software without restriction, including without limitation
  11 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
  12 // and/or sell copies of the Software, and to permit persons to whom the
  13 // Software is furnished to do so, subject to the following conditions:
  14 //
  15 // The above copyright notice and this permission notice shall be included in
  16 // all copies or substantial portions of the Software.
  17 //
  18 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  21 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  22 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  23 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  24 // DEALINGS IN THE SOFTWARE.
  25 //
  26
  27 using System;
  28 using System.IO;
  29 using System.Text;
  30
  31 using Beagle.Util;
  32 using Beagle.Daemon;
  33
  34 namespace Beagle.Filters {
  35
  36         public class FilterGif : FilterImage {
  37
  38                 enum GifBytes {
  39                         Trailer = 0x3b,
  40                         ImageBlockSeparator = 0x2c,
  41
  42                         BlockIntroducer = 0x21,
  43                         BlockTerminator = 0x00,
  44
  45                         GraphicControlExtension = 0xf9,
  46                         CommentExtension = 0xfe,
  47                         PlaintextExtension = 0x01,
  48                         ApplicationExtension = 0xff
  49                 }
  50
  51                 static public bool Debug = false;
  52
  53                 public FilterGif () : base ()
  54                 {
  55                         AddSupportedFlavor (FilterFlavor.NewFromMimeType ("image/gif"));
  56                 }
  57
  58                 protected override void PullImageProperties ()
  59                 {
  60                         try {
  61                                 /* Parse the GIF Header to get the version and overall size */
  62                                 byte [] data = new byte [13];
  63                                 Stream.Read (data, 0, data.Length);
  64
  65                                 if (data [0] != 'G' || data [1] != 'I' || data [2] != 'F') {
  66                                         Logger.Log.Debug ("File is not a GIF file!");
  67                                         Error ();
  68                                         return;
  69                                 }
  70
  71                                 char [] gif_version = { (char) data [3], (char) data [4], (char) data [5] };
  72
  73                                 AddProperty (Beagle.Property.NewUnsearched ("gif:version", new string (gif_version)));
  74
  75                                 ushort width = EndianConverter.ToUInt16 (data, 6, true);
  76                                 ushort height = EndianConverter.ToUInt16 (data, 8, true);
  77
  78                                 Width = width;
  79                                 Height = height;
  80
  81                                 /*
  82                                  * Everything from here onwards is for parsing the GIF Stream
  83                                  * and extracting comments and plaintext and working out how
  84                                  * many frames there are and how many times they are supposed
  85                                  * to loop.
  86                                 */
  87
  88                                 GifBytes gb;
  89                                 int b, num_frames = 0, ct_size;
  90
  91                                 if ((data [10] & 0x80) == 0x80) {
  92                                         /* A Global Color Table exists */
  93                                         ct_size = (int) (3 * Math.Pow(2, (data[10] & 0x07) + 1));
  94
  95                                         if (Debug)
  96                                                 Logger.Log.Debug ("ct_size: " + ct_size);
  97
  98                                         Stream.Seek (ct_size, SeekOrigin.Current);
  99                                 }
 100
 101                                 while ((gb = (GifBytes) Stream.ReadByte ()) != GifBytes.Trailer
 102                                        && (int) gb != -1) {
 103
 104                                         switch (gb) {
 105                                                 case GifBytes.ImageBlockSeparator:
 106                                                         num_frames++;
 107
 108                                                         if (Debug)
 109                                                                 Logger.Log.Debug ("Start of Image Block : " + Stream.Position);
 110
 111                                                         Stream.Seek (8, SeekOrigin.Current);
 112                                                         b = Stream.ReadByte ();
 113
 114                                                         if ((b & 0x80) == 0x80) {
 115                                                                 /* A Local Color Table exists */
 116
 117                                                                 ct_size = (int) (3 * Math.Pow(2, (b & 0x07) + 1));
 118
 119                                                                 if (Debug) {
 120                                                                         Logger.Log.Debug ("-- Image Block has local color table");
 121                                                                         Logger.Log.Debug ("ct_size: " + ct_size);
 122                                                                 }
 123
 124                                                                 Stream.Seek (ct_size, SeekOrigin.Current);
 125                                                         }
 126
 127                                                         Stream.ReadByte ();
 128                                                         while ((b = Stream.ReadByte ()) != 0x0) {
 129                                                                 if (Debug)
 130                                                                         Logger.Log.Debug ("-- Image Data Block size: " + b + " pos: " + Stream.Position);
 131
 132                                                                 if (b == -1) {
 133                                                                         Logger.Log.Warn ("Invalid Data Block size");
 134                                                                         Error ();
 135                                                                         return;
 136                                                                 }
 137
 138                                                                 Stream.Seek (b, SeekOrigin.Current);
 139                                                         }
 140
 141                                                         if (Debug)
 142                                                                 Logger.Log.Debug ("-- Image Block end: " + Stream.Position);
 143                                                         break;
 144
 145                                                 case GifBytes.BlockIntroducer:
 146                                                         if (Debug)
 147                                                                 Logger.Log.Debug ("Start of Extension : " + Stream.Position);
 148                                                         break;
 149
 150                                                 case GifBytes.GraphicControlExtension:
 151                                                         if (Debug)
 152                                                                 Logger.Log.Debug ("-- Graphic Control Extension : " + Stream.Position);
 153
 154                                                         Stream.Seek (6, SeekOrigin.Current);
 155                                                         break;
 156
 157                                                 case GifBytes.PlaintextExtension:
 158                                                         if (Debug)
 159                                                                 Logger.Log.Debug ("Plaintext Extension: " + Stream.Position);
 160
 161                                                         Stream.Seek (13, SeekOrigin.Current);
 162
 163                                                         while ((b = Stream.ReadByte ()) != 0x0) {
 164                                                                 if (Debug)
 165                                                                         Logger.Log.Debug ("-- Plaintext Data Block size: " + b + " pos: " + Stream.Position);
 166
 167                                                                 if (b == -1) {
 168                                                                         Logger.Log.Warn ("Invalid Plaintext Data Block size!");
 169                                                                         Error ();
 170                                                                         return;
 171                                                                 }
 172
 173                                                                 char [] cbuffer = new char [b];
 174
 175                                                                 for (int i = 0; i < b; i++)
 176                                                                         cbuffer [i] = (char) Stream.ReadByte ();
 177
 178                                                                 AppendText (new string (cbuffer));
 179
 180                                                                 if (Debug)
 181                                                                         Logger.Log.Debug ("-- Plaintext Data: " + new string(cbuffer));
 182                                                         }
 183
 184                                                         if (Debug)
 185                                                                 Logger.Log.Debug ("-- Plaintext Extension End: " + Stream.Position);
 186                                                         break;
 187
 188                                                 case GifBytes.CommentExtension:
 189                                                         if (Debug)
 190                                                                 Logger.Log.Debug ("Comment Extension: " + Stream.Position);
 191
 192                                                         while ((b = Stream.ReadByte ()) != 0x0) {
 193                                                                 if (Debug)
 194                                                                         Logger.Log.Debug ("-- Comment Data Block size: " + b + " pos: " + Stream.Position);
 195
 196                                                                 if (b == -1) {
 197                                                                         Logger.Log.Warn ("Invalid Comment Data Block size!");
 198                                                                         Error ();
 199                                                                         return;
 200                                                                 }
 201
 202                                                                 char [] cbuffer = new char [b];
 203
 204                                                                 for (int i = 0; i < b; i++) {
 205                                                                         cbuffer[i] = (char) Stream.ReadByte ();
 206                                                                 }
 207
 208                                                                 AppendText (new string (cbuffer));
 209
 210                                                                 if (Debug)
 211                                                                         Logger.Log.Debug ("-- Comment Data: " + new string(cbuffer));
 212                                                         }
 213
 214                                                         if (Debug)
 215                                                                 Logger.Log.Debug ("-- Comment Extension End: " + Stream.Position);
 216                                                         break;
 217
 218                                                 case GifBytes.ApplicationExtension:
 219                                                         if (Debug)
 220                                                                 Logger.Log.Debug ("Application Extension: " + Stream.Position);
 221
 222                                                         Stream.ReadByte ();
 223
 224                                                         char [] cbuffer = new char [11];
 225                                                         for (int i = 0; i < 11; i++) {
 226                                                                 cbuffer [i] = (char) Stream.ReadByte ();
 227                                                         }
 228
 229                                                         string application = new string (cbuffer);
 230
 231                                                         if (application == "NETSCAPE2.0") {
 232                                                                 if (Debug)
 233                                                                         Logger.Log.Debug ("-- Application: 'NETSCAPE2.0'>");
 234
 235                                                                 Stream.ReadByte ();
 236                                                                 Stream.ReadByte ();
 237
 238                                                                 b = Stream.ReadByte();
 239
 240                                                                 if (b == 0)
 241                                                                         AddProperty (Beagle.Property.NewUnsearched ("gif:loopcount", "infinite"));
 242                                                                 else
 243                                                                         AddProperty (Beagle.Property.NewUnsearched ("gif:loopcount", b));
 244
 245                                                                 Stream.ReadByte();
 246                                                         } else {
 247                                                                 //unknown extension...
 248                                                                 while ((b = Stream.ReadByte ()) != 0x0) {
 249                                                                         if (Debug)
 250                                                                                 Logger.Log.Debug ("-- Application Data Block size: " + b + " pos: " + Stream.Position);
 251
 252                                                                         if (b == -1) {
 253                                                                                 Logger.Log.Warn ("Invalid Application Data Block size!");
 254                                                                                 Error ();
 255                                                                                 return;
 256                                                                         }
 257
 258                                                                         Stream.Seek (b, SeekOrigin.Current);
 259                                                                 }
 260                                                         }
 261
 262                                                         if (Debug)
 263                                                                 Logger.Log.Debug ("-- Application Extension End: " + Stream.Position);
 264                                                         break;
 265
 266                                                 default:
 267                                                         break;
 268                                         }
 269                                 }
 270
 271                                 if (Debug && gb == GifBytes.Trailer)
 272                                         Logger.Log.Debug ("Trailer marker: " + Stream.Position);
 273
 274                                 // We got zero frames, this isn't actually a valid GIF file.
 275                                 if (num_frames == 0) {
 276                                         Logger.Log.Debug ("File doesn't contain any GIF frames");
 277                                         Error ();
 278                                         return;
 279                                 }
 280
 281                                 AddProperty (Beagle.Property.NewUnsearched ("gif:numframes", num_frames));
 282                         } catch (Exception e) {
 283                                 if (Debug)
 284                                         Logger.Log.Debug ("-- Exception: {0} - {1}", Stream.Position, e);
 285                                 Error ();
 286                         }
 287                 }
 288         }
 289 }