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                 public FilterGif () : base ()
  52                 {
  53                         AddSupportedFlavor (FilterFlavor.NewFromMimeType ("image/gif"));
  54                 }
  55
  56                 protected override void PullImageProperties ()
  57                 {
  58                         try {
  59                                 /* Parse the GIF Header to get the version and overall size */
  60                                 byte [] data = new byte [13];
  61                                 Stream.Read (data, 0, data.Length);
  62
  63                                 ushort width = EndianConverter.ToUInt16 (data, 6, true);
  64                                 ushort height = EndianConverter.ToUInt16 (data, 8, true);
  65
  66                                 char [] gif_version = { (char) data [3], (char) data [4], (char) data [5] };
  67
  68                                 AddProperty (Beagle.Property.NewUnsearched ("gif:version", new string (gif_version)));
  69
  70                                 Width = width;
  71                                 Height = height;
  72
  73                                 /*
  74                                  * Everything from here onwards is for parsing the GIF Stream
  75                                  * and extracting comments and plaintext and working out how
  76                                  * many frames there are and how many times they are supposed
  77                                  * to loop.
  78                                 */
  79
  80                                 GifBytes gb;
  81                                 int b, num_frames = 0, ct_size;
  82
  83                                 if ((data [10] & 0x80) == 0x80) {
  84                                         /* A Global Color Table exists */
  85                                         ct_size = (int) (3 * Math.Pow(2, (data[10] & 0x07) + 1));
  86                                         //System.Console.WriteLine("ct_size: " + ct_size);
  87                                         Stream.Seek (ct_size, SeekOrigin.Current);
  88                                 }
  89
  90                                 while ((gb = (GifBytes) Stream.ReadByte ()) != GifBytes.Trailer) {
  91                                         switch (gb) {
  92                                                 case GifBytes.ImageBlockSeparator:
  93                                                         num_frames++;
  94
  95                                                         //System.Console.WriteLine("Start of Image Block : " + Stream.Position);
  96
  97                                                         Stream.Seek (8, SeekOrigin.Current);
  98                                                         b = Stream.ReadByte ();
  99
 100                                                         if ((b & 0x80) == 0x80) {
 101                                                                 /* A Local Color Table exists */
 102                                                                 //System.Console.WriteLine("-- Image Block has local color table");
 103                                                                 ct_size = (int) (3 * Math.Pow(2, (b & 0x07) + 1));
 104                                                                 //System.Console.WriteLine("ct_size: " + ct_size);
 105                                                                 Stream.Seek (ct_size, SeekOrigin.Current);
 106                                                         }
 107
 108                                                         Stream.ReadByte ();
 109                                                         while ((b = Stream.ReadByte ()) != 0x0) {
 110                                                                 //System.Console.WriteLine("-- Image Data Block size: " + b + " pos: " + Stream.Position);
 111                                                                 Stream.Seek (b, SeekOrigin.Current);
 112                                                         }
 113
 114                                                         //System.Console.WriteLine("-- Image Block end: " + Stream.Position);
 115                                                         break;
 116
 117                                                 case GifBytes.BlockIntroducer:
 118                                                         //System.Console.WriteLine("Start of Extension : " + Stream.Position);
 119                                                         break;
 120
 121                                                 case GifBytes.GraphicControlExtension:
 122                                                         //System.Console.WriteLine("-- Graphic Control Extension : " + Stream.Position);
 123                                                         Stream.Seek (6, SeekOrigin.Current);
 124                                                         break;
 125
 126                                                 case GifBytes.PlaintextExtension:
 127                                                         //System.Console.WriteLine("Plaintext Extension: " + Stream.Position);
 128
 129                                                         Stream.Seek (13, SeekOrigin.Current);
 130
 131                                                         while ((b = Stream.ReadByte ()) != 0x0) {
 132                                                                 //System.Console.WriteLine("-- Plaintext Data Block size: " + b + " pos: " + Stream.Position);
 133                                                                 char [] cbuffer = new char [b];
 134
 135                                                                 for (int i = 0; i < b; i++)
 136                                                                         cbuffer [i] = (char) Stream.ReadByte ();
 137
 138                                                                 AppendText (new string (cbuffer));
 139                                                                 //System.Console.WriteLine("-- Plaintext Data: " + new string(cbuffer));
 140                                                         }
 141
 142                                                         //System.Console.WriteLine("-- Plaintext Extension End: " + Stream.Position);
 143                                                         break;
 144
 145                                                 case GifBytes.CommentExtension:
 146                                                         //System.Console.WriteLine("Comment Extension: " + Stream.Position);
 147
 148                                                         while ((b = Stream.ReadByte ()) != 0x0) {
 149                                                                 //System.Console.WriteLine("-- Comment Data Block size: " + b + " pos: " + Stream.Position);
 150                                                                 char [] cbuffer = new char [b];
 151
 152                                                                 for (int i = 0; i < b; i++) {
 153                                                                         cbuffer[i] = (char) Stream.ReadByte ();
 154                                                                 }
 155
 156                                                                 AppendText (new string (cbuffer));
 157                                                                 //System.Console.WriteLine("-- Comment Data: " + new string(cbuffer));
 158                                                         }
 159
 160                                                         //System.Console.WriteLine("-- Comment Extension End: " + Stream.Position);
 161                                                         break;
 162
 163                                                 case GifBytes.ApplicationExtension:
 164                                                         //System.Console.WriteLine("Application Extension: " + Stream.Position);
 165
 166                                                         Stream.ReadByte ();
 167
 168                                                         char [] cbuffer = new char [11];
 169                                                         for (int i = 0; i < 11; i++) {
 170                                                                 cbuffer [i] = (char) Stream.ReadByte ();
 171                                                         }
 172
 173                                                         string application = new string (cbuffer);
 174
 175                                                         if (application == "NETSCAPE2.0") {
 176                                                                 //System.Console.WriteLine("-- Application: 'NETSCAPE2.0'>");
 177
 178                                                                 Stream.ReadByte ();
 179                                                                 Stream.ReadByte ();
 180
 181                                                                 b = Stream.ReadByte();
 182
 183                                                                 if (b == 0)
 184                                                                         AddProperty (Beagle.Property.NewUnsearched ("gif:loopcount", "infinite"));
 185                                                                 else
 186                                                                         AddProperty (Beagle.Property.NewUnsearched ("gif:loopcount", b));
 187
 188                                                                 Stream.ReadByte();
 189                                                         } else {
 190                                                                 //unknown extension...
 191                                                                 while ((b = Stream.ReadByte ()) != 0x0) {
 192                                                                         //System.Console.WriteLine("-- Application Data Block size: " + b + " pos: " + Stream.Position);
 193                                                                         Stream.Seek (b, SeekOrigin.Current);
 194                                                                 }
 195                                                         }
 196                                                         //System.Console.WriteLine("-- Application Extension End: " + Stream.Position);
 197                                                         break;
 198
 199                                                 default:
 200                                                         break;
 201                                         }
 202                                 }
 203                                 AddProperty (Beagle.Property.NewUnsearched ("gif:numframes", num_frames));
 204                         } catch (Exception) {
 205                                 //System.Console.WriteLine("-- Exception! " + Stream.Position);
 206                                 Error ();
 207                         }
 208                 }
 209         }
 210 }