Source for gnu.javax.imageio.bmp.BMPDecoder

   1: /* BMPDecoder.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.nio.ByteBuffer;
  43: import java.nio.ByteOrder;
  44: import java.awt.image.IndexColorModel;
  45: import java.awt.image.BufferedImage;
  46: 
  47: public abstract class BMPDecoder {
  48: 
  49:     protected BMPInfoHeader infoHeader;
  50:     protected BMPFileHeader fileHeader;
  51:     protected long offset;
  52: 
  53:     public BMPDecoder(BMPFileHeader fh, BMPInfoHeader ih){
  54:         fileHeader = fh;
  55:         infoHeader = ih;
  56:         offset = BMPFileHeader.SIZE + BMPInfoHeader.SIZE;
  57:     }
  58: 
  59:     /**
  60:      * Determines the coding type of the bitmap and returns the corresponding
  61:      * decoder.
  62:      */
  63:     public static BMPDecoder getDecoder(BMPFileHeader fh, BMPInfoHeader ih){
  64:         switch(ih.getCompression()){
  65:         case BMPInfoHeader.BI_RGB: // uncompressed RGB
  66:             switch(ih.getBitCount()){
  67:             case 32:
  68:                 return new DecodeBF32(fh, ih, true);
  69: 
  70:             case 24:
  71:                 return new DecodeRGB24(fh, ih);
  72: 
  73:             case 16:
  74:                 return new DecodeBF16(fh, ih, true);
  75: 
  76:             case 8:
  77:                 return new DecodeRGB8(fh, ih);
  78: 
  79:             case 4:
  80:                 return new DecodeRGB4(fh, ih);
  81: 
  82:             case 1:
  83:                 return new DecodeRGB1(fh, ih);
  84: 
  85:             default:
  86:                 return null;
  87:             }
  88: 
  89:         case BMPInfoHeader.BI_RLE8:
  90:             return new DecodeRLE8(fh, ih);
  91: 
  92:         case BMPInfoHeader.BI_RLE4:
  93:             return new DecodeRLE4(fh, ih);
  94: 
  95:         case BMPInfoHeader.BI_BITFIELDS:
  96:             switch(ih.getBitCount()){
  97:             case 16:
  98:                 return new DecodeBF16(fh, ih, false);
  99: 
 100:             case 32:
 101:                 return new DecodeBF32(fh, ih, false);
 102: 
 103:             default:
 104:                 return null;
 105:             }
 106: 
 107:         default:
 108:             return null;
 109:         }
 110:     }
 111: 
 112:     /**
 113:      * The image decoder.
 114:      */
 115:     public abstract BufferedImage decode(ImageInputStream in)
 116:         throws IOException, BMPException;
 117: 
 118:     /**
 119:      * Reads r,g,b bit masks from an inputstream
 120:      */
 121:     protected int[] readBitMasks(ImageInputStream in) throws IOException {
 122:         int[] bitmasks = new int[3];
 123:         byte[] temp = new byte[12];
 124:         if(in.read(temp) != 12)
 125:             throw new IOException("Couldn't read bit masks.");
 126:         offset += 12;
 127: 
 128:         ByteBuffer buf = ByteBuffer.wrap(temp);
 129:         buf.order(ByteOrder.LITTLE_ENDIAN);
 130:         bitmasks[0] = buf.getInt();
 131:         bitmasks[1] = buf.getInt();
 132:         bitmasks[2] = buf.getInt();
 133:         return bitmasks;
 134:     }
 135: 
 136:     /**
 137:      * Reads an N-color palette from an inputstream in RGBQUAD format and
 138:      * returns an equivalent ColorModel object
 139:      */
 140:     protected IndexColorModel readPalette(ImageInputStream in) throws IOException {
 141:         int N = infoHeader.getNumberOfPaletteEntries();
 142:         byte[] r = new byte[N];
 143:         byte[] g = new byte[N];
 144:         byte[] b = new byte[N];
 145:         for(int i=0;i<N;i++){
 146:             byte[] RGBquad = new byte[4];
 147:             if(in.read(RGBquad) != 4)
 148:                 throw new IOException("Error reading palette information.");
 149:             // RGBQUAD structure is b,g,r,0
 150:             r[i] = RGBquad[2];
 151:             g[i] = RGBquad[1];
 152:             b[i] = RGBquad[0];
 153:         }
 154: 
 155:         offset += 4*N;
 156:         return new IndexColorModel(8, N, r, g, b);
 157:     }
 158: 
 159:     /**
 160:      * Read bytes to the start of the image data
 161:      */
 162:     protected void skipToImage(ImageInputStream in) throws IOException {
 163:         byte[] d = new byte[1];
 164:         long n = fileHeader.getOffset() - offset;
 165:         for(int i=0;i<n;i++)
 166:             in.read(d);
 167:     }
 168: }