gomp-20050608-branch/libjava/classpath/gnu/javax/imageio/bmp/DecodeRLE4.java

   1 /* DecodeRLE4.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.MultiPixelPackedSampleModel;
  49 import java.awt.image.SampleModel;
  50 import java.awt.Dimension;
  51
  52 public class DecodeRLE4 extends BMPDecoder {
  53
  54     public DecodeRLE4(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 MultiPixelPackedSampleModel(DataBuffer.TYPE_BYTE,
  76                                                          w, h, 4);
  77
  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>>1];
  88         int offIn = 0;
  89         int x=0,y=0;
  90
  91         // width in bytes
  92         w += (w&1);
  93         w = w >> 1;
  94
  95         try {
  96             while(((x>>1) + y*w) < w*h){
  97                 if(in.read(cmd) != 2)
  98                     throw new IOException("Error reading compressed data.");
  99
 100                 if(cmd[0] == ESCAPE){
 101                     switch(cmd[1]){
 102                     case EOB: // end of bitmap
 103                         return data;
 104                     case EOL: // end of line
 105                         x = 0;
 106                         y++;
 107                         break;
 108                     case DELTA: // delta
 109                         if(in.read(cmd) != 2)
 110                             throw new IOException("Error reading compressed data.");
 111                         int dx = cmd[0] & (0xFF);
 112                         int dy = cmd[1] & (0xFF);
 113                         x += dx;
 114                         y += dy;
 115                         break;
 116
 117                     default:
 118                         // decode a literal run
 119                         int length = cmd[1] & (0xFF);
 120
 121                         // size of run, which is word aligned.
 122                         int bytesize = length;
 123                         bytesize += (bytesize & 1);
 124                         bytesize >>= 1;
 125                         bytesize += (bytesize & 1);
 126
 127                         byte[] run = new byte[bytesize];
 128                         if(in.read(run) != bytesize)
 129                             throw new IOException("Error reading compressed data.");
 130
 131                         if((x&1) == 0){
 132                             length += (length&1);
 133                             length >>= 1;
 134                             System.arraycopy(run, 0, data, ((x>>1) + w*(h-y-1)),
 135                                              length);
 136                         } else {
 137                             for(int i=0;i<length;i++){
 138                                 if((i&1) == 0) // copy high to low
 139                                     data[((x+i)>>1) + w*(h-y-1)]
 140                                         |= ((run[i>>1]&0xF0) >> 4);
 141                                 else  // copy low to high
 142                                     data[((x+i)>>1) + w*(h-y-1)]
 143                                         |= ((run[i>>1]&0x0F) << 4);
 144                             }
 145                         }
 146                         x += cmd[1] & (0xFF);
 147                         break;
 148                     }
 149                 } else {
 150                     // decode a byte run
 151                     int length = cmd[0] & (0xFF);
 152                     if((x&1) == 0){
 153                         length += (length&1);
 154                         length >>= 1;
 155                         for(int i=0;i<length;i++)
 156                             data[(h-y-1)*w + i + (x >> 1)] = cmd[1];
 157                     } else {
 158                         for(int i=0;i<length;i++){
 159                             if((i&1) == 0) // copy high to low
 160                                 data[((x+i)>>1) + w*(h-y-1)]
 161                                     |= ((cmd[1]&0xF0) >> 4);
 162                             else  // copy low to high
 163                                 data[((x+i)>>1) + w*(h-y-1)]
 164                                     |= ((cmd[1]&0x0F) << 4);
 165                         }
 166                     }
 167                     x += cmd[0] & (0xFF);
 168                 }
 169             }
 170             return data;
 171         } catch(ArrayIndexOutOfBoundsException e){
 172             throw new BMPException("Invalid RLE data.");
 173         }
 174     }
 175 }
 176