Source for gnu.javax.imageio.png.PNGDecoder

   1: /* PNGDecoder.java
   2:    Copyright (C) 2006 Free Software Foundation
   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.png;
  39: 
  40: import java.util.zip.Inflater;
  41: import java.util.zip.DataFormatException;
  42: import java.awt.image.ColorModel;
  43: import java.awt.image.ComponentColorModel;
  44: import java.awt.image.ComponentSampleModel;
  45: import java.awt.image.DataBuffer;
  46: import java.awt.image.DataBufferByte;
  47: import java.awt.image.DataBufferUShort;
  48: import java.awt.image.IndexColorModel;
  49: import java.awt.image.MultiPixelPackedSampleModel;
  50: import java.awt.image.Raster;
  51: import java.awt.image.SampleModel;
  52: import java.awt.image.SinglePixelPackedSampleModel;
  53: import java.awt.image.WritableRaster;
  54: import java.awt.color.ColorSpace;
  55: 
  56: public class PNGDecoder
  57: {
  58:   private PNGHeader header;
  59:   private byte[] raster;
  60:   private byte[] scanline, lastScanline;
  61:   private byte[] filterType;
  62:   private int offset, length;
  63:   private int currentScanline;
  64:   private final int stride;
  65:   private Inflater inflater;
  66:   private boolean readFilter;
  67:   private int bpp; // bytes per pixel
  68: 
  69:   /**
  70:    * Constructs a filter object for
  71:    */
  72:   public PNGDecoder(PNGHeader header)
  73:   {
  74:     this.header = header;
  75:     offset = 0;
  76:     inflater = new Inflater();
  77:     stride = header.getScanlineStride();
  78:     length = stride * header.getHeight();
  79: 
  80:     // Allocate the output raster
  81:     raster = new byte[ length ];
  82:     scanline = new byte[ stride ];
  83:     lastScanline = new byte[ stride ];
  84:     currentScanline = 0;
  85:     readFilter = true;
  86:     bpp = header.bytesPerPixel();
  87:     filterType = new byte[1];
  88:     inflater = new Inflater();
  89:   }
  90: 
  91:   private int getBytes( byte[] buf, int offset ) throws PNGException
  92:   {
  93:     try
  94:       {
  95:     return inflater.inflate( buf, offset, buf.length - offset);
  96:       }
  97:     catch(DataFormatException dfe)
  98:       {
  99:     throw new PNGException("Error inflating data.");
 100:       }
 101:   }
 102: 
 103:   /**
 104:    * Decodes a data chunk.
 105:    */
 106:   public void addData( PNGData chunk ) throws PNGException
 107:   {
 108:     int n = 0;
 109:     if( isFinished() )
 110:       return;
 111:     chunk.feedToInflater( inflater );
 112:     do
 113:       {
 114:     if( readFilter )
 115:       if( getBytes( filterType, 0 ) < 1 )
 116:         return;
 117: 
 118:     n = getBytes( scanline, offset );
 119: 
 120:     if( offset + n < stride )
 121:       {
 122:         offset += n;
 123:         readFilter = false;
 124:       }
 125:     else
 126:       {
 127:         scanline = PNGFilter.unFilterScanline( filterType[0], scanline,
 128:                            lastScanline, bpp );
 129:         System.arraycopy( scanline, 0,
 130:                   raster, currentScanline * stride, stride );
 131:         lastScanline = scanline;
 132:         scanline = new byte[scanline.length];
 133:         currentScanline++;
 134:         readFilter = true;
 135:         offset = 0;
 136:       }
 137:       }
 138:     while( n > 0 && currentScanline < header.getHeight() );
 139:   }
 140: 
 141:   /**
 142:    * Parse the appropriate color type and create an AWT raster for it.
 143:    * @param header - the file header.
 144:    */
 145:   public WritableRaster getRaster( PNGHeader header )
 146:   {
 147:     SampleModel sm = null;
 148:     DataBuffer db = null;
 149:     int t;
 150:     int width = header.getWidth();
 151:     int height = header.getHeight();
 152:     int depth = header.getDepth();
 153: 
 154:     switch( header.getColorType() )
 155:       {
 156:       case PNGHeader.GRAYSCALE_WITH_ALPHA:
 157:     if( depth == 8 )
 158:       {
 159:         t = DataBuffer.TYPE_BYTE;
 160:         db = getByteBuffer();
 161:       }
 162:     else
 163:       { 
 164:         t = DataBuffer.TYPE_USHORT;
 165:         db = getShortBuffer();
 166:       }
 167:     sm = new ComponentSampleModel(t, width, height, 2, width * 2,
 168:                       new int[]{0, 1});
 169:     break;
 170: 
 171:       case PNGHeader.GRAYSCALE:
 172:     switch( depth )
 173:       {
 174:       case 16:
 175:         sm = new ComponentSampleModel(DataBuffer.TYPE_USHORT, 
 176:                       width, height, 1, width,
 177:                       new int[]{ 0 });
 178:         db = getShortBuffer();
 179:         break;
 180:         
 181:       case 8:
 182:         sm = new ComponentSampleModel(DataBuffer.TYPE_BYTE, 
 183:                       width, height, 1, width,
 184:                       new int[]{ 0 });
 185:         db = getByteBuffer();
 186:         break;
 187:         
 188:       default:
 189:         sm = new MultiPixelPackedSampleModel(DataBuffer.TYPE_BYTE, 
 190:                          width, height, depth);
 191:         db = getByteBuffer();
 192:         break;
 193:       }
 194:     break;
 195: 
 196:       case PNGHeader.RGB:
 197:     if( depth == 8 )
 198:       {
 199:         t = DataBuffer.TYPE_BYTE;
 200:         db = getByteBuffer();
 201:       }
 202:     else
 203:       { 
 204:         t = DataBuffer.TYPE_USHORT;
 205:         db = getShortBuffer();
 206:       }
 207:     sm = new ComponentSampleModel(t, width, height, 3, 3 * width,
 208:                       new int[]{0, 1, 2});
 209:     break;
 210: 
 211:       case PNGHeader.RGB_WITH_ALPHA:
 212:     if( depth == 8 )
 213:       {
 214:         t = DataBuffer.TYPE_BYTE;
 215:         db = getByteBuffer();
 216:       }
 217:     else
 218:       { 
 219:         t = DataBuffer.TYPE_USHORT;
 220:         db = getShortBuffer();
 221:       }
 222:     
 223:     sm = new ComponentSampleModel(t, width, height, 4, width * 4,
 224:                       new int[]{0, 1, 2, 3});
 225:     break;
 226:     
 227:       case PNGHeader.INDEXED:
 228:     if( depth == 8 )
 229:       sm = new SinglePixelPackedSampleModel(DataBuffer.TYPE_BYTE, 
 230:                         width, height, 
 231:                         new int[] {0xFF});
 232:     else
 233:       sm = new MultiPixelPackedSampleModel(DataBuffer.TYPE_BYTE, 
 234:                            width, height, depth);
 235:     db = getByteBuffer();
 236:     break;
 237:       }
 238: 
 239:     return Raster.createWritableRaster(sm, db, null);
 240:   }
 241: 
 242:   /**
 243:    * Wrap the raster with a DataBufferUShort,
 244:    * conversion is big-endian (PNG native).
 245:    */
 246:   private DataBuffer getShortBuffer()
 247:   {
 248:     short[] data = new short[(raster.length >> 1)];
 249:     for( int i = 0; i < data.length; i++ )
 250:       data[i] = (short)(((raster[i * 2] & 0xFF) << 8) | 
 251:             (raster[i * 2 + 1] & 0xFF));
 252:     return new DataBufferUShort( data, data.length );
 253:   }
 254: 
 255:   /**
 256:    * Wrap the raster with a DataBufferByte
 257:    */
 258:   private DataBuffer getByteBuffer()
 259:   {
 260:     return new DataBufferByte( raster, raster.length );
 261:   }
 262: 
 263:   public ColorModel getColorModel( ColorSpace cs, 
 264:                    int colorType, int depth )
 265:   {
 266:     int[] bits;
 267:     boolean hasAlpha = false;
 268:     int transferType;
 269: 
 270:     switch( colorType )
 271:       {
 272:       case PNGHeader.GRAYSCALE_WITH_ALPHA:
 273:     if( cs == null )
 274:       cs = ColorSpace.getInstance( ColorSpace.CS_GRAY );
 275:     hasAlpha = true;
 276:     bits = new int[]{ depth, depth };
 277:     break;
 278:     
 279:       case PNGHeader.RGB:
 280:     bits = new int[]{ depth, depth, depth };
 281:     break;
 282: 
 283:       case PNGHeader.RGB_WITH_ALPHA:
 284:     hasAlpha = true;
 285:     bits = new int[]{ depth, depth, depth, depth };
 286:     break;
 287: 
 288:       case PNGHeader.GRAYSCALE:
 289:     if( depth < 8 )
 290:       return grayPalette( depth );
 291: 
 292:     if( cs == null )
 293:       cs = ColorSpace.getInstance( ColorSpace.CS_GRAY );
 294:     bits = new int[]{ depth };
 295:     break;
 296: 
 297:       default:
 298:       case PNGHeader.INDEXED:
 299:     return null; // Handled by the palette chunk.
 300:       }
 301: 
 302:     if( cs == null )
 303:       cs = ColorSpace.getInstance( ColorSpace.CS_sRGB );
 304: 
 305: 
 306:     return new ComponentColorModel(cs, bits, hasAlpha, false, 
 307:                    (hasAlpha ? 
 308:                     ComponentColorModel.TRANSLUCENT : 
 309:                     ComponentColorModel.OPAQUE), 
 310:                    ((depth == 16) ? DataBuffer.TYPE_USHORT : 
 311:                     DataBuffer.TYPE_BYTE));
 312:   }
 313: 
 314:   private IndexColorModel grayPalette(int depth)
 315:   { 
 316:     byte[] c = new byte[ (1 << depth) ];
 317:     for(int i = 0; i < c.length; i++)
 318:       c[i] = (byte)(255.0 * (((double)i) / ((double)c.length - 1.0)));
 319:     return new IndexColorModel(8, c.length, c, c, c);
 320:   }
 321: 
 322:   public byte[] getRaster()
 323:   {
 324:     return raster;
 325:   }
 326: 
 327:   public boolean isFinished()
 328:   {
 329:     return currentScanline >= header.getHeight();
 330:   }
 331: }