Source for gnu.javax.imageio.jpeg.JPEGImageInputStream

   1: /* JPEGImageInputStream.java --
   2:    Copyright (C)  2006  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: package gnu.javax.imageio.jpeg;
  39: 
  40: import java.io.EOFException;
  41: import java.io.IOException;
  42: import javax.imageio.*;
  43: import javax.imageio.spi.*;
  44: import javax.imageio.metadata.*;
  45: import javax.imageio.stream.ImageInputStream;
  46: import javax.imageio.stream.ImageInputStreamImpl;
  47: 
  48: import java.util.Iterator;
  49: import java.awt.image.BufferedImage;
  50: 
  51: public class JPEGImageInputStream
  52:   extends ImageInputStreamImpl
  53: {
  54:   private ImageInputStream in;
  55: 
  56:   byte marker;
  57:   
  58:   public JPEGImageInputStream(ImageInputStream in)
  59:   {
  60:     super();
  61: 
  62:     this.in = in;
  63:   }
  64: 
  65:   public int read()
  66:     throws IOException
  67:   {
  68:     setBitOffset(0);
  69:     return in.read();
  70:   }
  71: 
  72:   public int read(byte[] data, int offset, int len)
  73:     throws IOException
  74:   {
  75:     setBitOffset(0);
  76:     return in.read(data, offset, len);
  77:   }
  78:   
  79:   /**
  80:    * Pull a byte from the stream, this checks to see if the byte is 0xff
  81:    * and if the next byte isn't 0x00 (stuffed byte) it errors out. If it's
  82:    * 0x00 then it simply ignores the byte.
  83:    *
  84:    * @return the next byte in the buffer
  85:    *
  86:    * @throws IOException TODO
  87:    * @throws BitStreamException TODO
  88:    */
  89:   private byte pullByte() throws IOException, JPEGMarkerFoundException
  90:   {
  91:     byte mybyte = readByte();
  92:     // FIXME: handle multiple 0xff in a row
  93:     if(mybyte==(byte)(0xff))
  94:       {
  95:         byte secondbyte = readByte();
  96:         if(secondbyte != (byte)(0x00))
  97:           {
  98:             marker = secondbyte;
  99:             throw new JPEGMarkerFoundException();
 100:           }
 101:       }
 102:     return mybyte;
 103:   }
 104: 
 105:   /**
 106:    * This returns the marker that was last encountered.  This should only be
 107:    * used if removeBit() throws a MarkerTagFound exception.
 108:    *
 109:    * @return marker as byte
 110:    */
 111:   public byte getMarker()
 112:   {
 113:     return marker;
 114:   }
 115: 
 116:   /**
 117:    * Removes a bit from the buffer. (Removes from the top of a queue). This
 118:    * also checks for markers and throws MarkerTagFound exception if it does.
 119:    * If MarkerTagFound is thrown you can use getMarker() method to get the
 120:    * marker that caused the throw.
 121:    *
 122:    * @param l specifies how many bits you want to remove and add to the
 123:    *        integer
 124:    * @return the amount of bits specified by l as an integer
 125:    *
 126:    * @throws IOException TODO
 127:    * @throws JPEGMarkerFoundException 
 128:    * @throws BitStreamException TODO
 129:    */
 130:   public int readBit()
 131:   throws IOException, JPEGMarkerFoundException
 132: {
 133:   checkClosed();
 134: 
 135:   // Calc new bit offset here, readByte resets it.
 136:   int newOffset = (bitOffset + 1) & 0x7;
 137: 
 138:   byte data = pullByte();
 139:   
 140:   if (bitOffset != 0)
 141:     {
 142:         seek(getStreamPosition() - 1);
 143:         data = (byte) (data >> (8 - newOffset));
 144:     }
 145: 
 146:   bitOffset = newOffset;
 147:   return data & 0x1;
 148: }
 149: 
 150: 
 151:   /**
 152:    * This method skips over the the data and finds the next position
 153:    * in the bit sequence with a X'FF' X'??' sequence.  Multiple X'FF
 154:    * bytes in sequence are considered padding and interpreted as one
 155:    * X'FF byte.
 156:    *
 157:    * @return the next marker byte in the stream
 158:    * @throws IOException if the end of the stream is reached
 159:    * unexpectedly
 160:    */
 161:   public byte findNextMarker()
 162:     throws IOException
 163:   {
 164:     boolean marked0xff = false;
 165:     byte byteinfo = JPEGMarker.X00;
 166: 
 167:     setBitOffset(0);
 168:     while (true)
 169:       {
 170:         byteinfo = readByte();
 171:         if (!marked0xff)
 172:           {
 173:             if (byteinfo == JPEGMarker.XFF)
 174:               marked0xff = true;
 175:           }
 176:         else
 177:           {
 178:             if (byteinfo == JPEGMarker.XFF)
 179:               // Ignore the value 0xff when it is immediately
 180:               // followed by another 0xff byte.
 181:               continue;
 182:             else if (byteinfo == JPEGMarker.X00)
 183:               // The sequence 0xff 0x00 is used to encode the
 184:               // actual value 0xff.  So restart our search for a
 185:               // marker.
 186:               marked0xff = false;
 187:             else
 188:               // One or more 0xff values were follwed by a
 189:               // non-0x00, non-0xff value so return this as the
 190:               // marker byte.
 191:               return byteinfo;
 192:           }
 193:       }
 194:   }
 195: }