libjava/classpath/gnu/javax/imageio/bmp/DecodeRLE8.java

   1 /* DecodeRLE8.java --
   2    Copyright (C)  2005  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.bmp;
  39
  40 import java.io.IOException;
  41 import javax.imageio.stream.ImageInputStream;
  42 import java.awt.image.BufferedImage;
  43 import java.awt.image.IndexColorModel;
  44 import java.awt.image.Raster;
  45 import java.awt.image.WritableRaster;
  46 import java.awt.image.DataBuffer;
  47 import java.awt.image.DataBufferByte;
  48 import java.awt.image.SinglePixelPackedSampleModel;
  49 import java.awt.image.SampleModel;
  50 import java.awt.Dimension;
  51
  52 public class DecodeRLE8 extends BMPDecoder {
  53
  54     public DecodeRLE8(BMPFileHeader fh, BMPInfoHeader ih){
  55         super(fh, ih);
  56     }
  57
  58     /**
  59      * RLE control codes
  60      */
  61     private static final byte ESCAPE = (byte)0;
  62     private static final byte EOL = (byte)0; // end of line
  63     private static final byte EOB = (byte)1; // end of bitmap
  64     private static final byte DELTA = (byte)2; // delta
  65
  66     public BufferedImage decode(ImageInputStream in) throws IOException, BMPException {
  67         IndexColorModel palette = readPalette(in);
  68         skipToImage(in);
  69
  70         Dimension d = infoHeader.getSize();
  71         int h = (int)d.getHeight();
  72         int w = (int)d.getWidth();
  73
  74         byte[] data = uncompress(w, h, in);
  75         SampleModel sm = new SinglePixelPackedSampleModel(DataBuffer.TYPE_BYTE,
  76                                                           w, h,
  77                                                           new int[] {0xFF});
  78         DataBuffer db = new DataBufferByte(data, w*h, 0);
  79         WritableRaster raster = Raster.createWritableRaster(sm, db, null);
  80
  81         return new BufferedImage(palette, raster, false, null);
  82     }
  83
  84     private byte[] uncompress(int w, int h, ImageInputStream in)
  85         throws BMPException, IOException {
  86         byte[] cmd = new byte[2];
  87         byte[] data = new byte[w*h];
  88         int offIn = 0;
  89         int x=0,y=0;
  90
  91         try {
  92             while((x + y*w) < w*h){
  93                 if(in.read(cmd) != 2)
  94                     throw new IOException("Error reading compressed data.");
  95
  96                 if(cmd[0] == ESCAPE){
  97                     switch(cmd[1]){
  98                     case EOB: // end of bitmap
  99                         return data;
 100                     case EOL: // end of line
 101                         x = 0;
 102                         y++;
 103                         break;
 104                     case DELTA: // delta
 105                         if(in.read(cmd) != 2)
 106                             throw new IOException("Error reading compressed data.");
 107                         int dx = cmd[0] & (0xFF);
 108                         int dy = cmd[1] & (0xFF);
 109                         x += dx;
 110                         y += dy;
 111                         break;
 112
 113                     default:
 114                         // decode a literal run
 115                         int length = cmd[1] & (0xFF);
 116                         int copylength = length;
 117
 118                         // absolute mode must be word-aligned
 119                         length += (length & 1);
 120
 121                         byte[] run = new byte[length];
 122                         if(in.read(run) != length)
 123                             throw new IOException("Error reading compressed data.");
 124
 125                         System.arraycopy(run, 0, data, (x+w*(h-y-1)),
 126                                          copylength);
 127                         x += copylength;
 128                         break;
 129                     }
 130                 } else {
 131                     // decode a byte run
 132                     int length = cmd[0] & (0xFF);
 133                     for(int i=0;i<length;i++)
 134                         data[(h-y-1)*w + x++] = cmd[1];
 135                 }
 136             }
 137             return data;
 138         } catch(ArrayIndexOutOfBoundsException e){
 139             throw new BMPException("Invalid RLE data.");
 140         }
 141     }
 142 }
 143