Source for gnu.javax.imageio.bmp.DecodeRLE4

   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: }