Java Source Code: 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 raster - 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:}