Source for gnu.javax.imageio.png.PNGImageReaderSpi

   1: /* PNGImageReaderSpi.java -- The ImageReader service provider for PNG
   2:    Copyright (C) 2006 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: 
  39: package gnu.javax.imageio.png;
  40: 
  41: import java.io.IOException;
  42: import java.io.InputStream;
  43: import java.util.Locale;
  44: 
  45: import javax.imageio.ImageReader;
  46: import javax.imageio.spi.ImageReaderSpi;
  47: import javax.imageio.stream.ImageInputStream;
  48: 
  49: /**
  50:  * The ImageIO ImageReader service provider for PNG images.
  51:  *
  52:  * @author Roman Kennke (kennke@aicas.com)
  53:  */
  54: public class PNGImageReaderSpi
  55:   extends ImageReaderSpi
  56: {
  57: 
  58:   /**
  59:    * The PNG file signature.
  60:    */
  61:   private static final byte[] SIGNATURE = new byte[]
  62:                               { (byte) 137, 80, 78, 71, 13, 10, 26, 10 };
  63: 
  64:   private static final String VENDOR_NAME = "GNU";
  65:   static final String VERSION = "1.0";
  66:   static final String READER_CLASSNAME =
  67:                                        "gnu.javax.imageio.png.PNGImageReader";
  68:   static final String[] NAMES = { "Portable Network Graphics" };
  69:   static final String[] SUFFIXES = { ".png" , ".PNG" };
  70:   static final String[] MIME_TYPES = { "image/png" };
  71:   static final String[] WRITER_SPI_NAMES =
  72:     new String[] { "gnu.javax.imageio.png.PNGWriterSpi" };
  73:   static final Class[] INPUT_TYPES = new Class[]{ InputStream.class,
  74:                                                   ImageInputStream.class};
  75:   public PNGImageReaderSpi()
  76:   {
  77:     super(VENDOR_NAME, VERSION, NAMES, SUFFIXES, MIME_TYPES, READER_CLASSNAME,
  78:           INPUT_TYPES, WRITER_SPI_NAMES, false, null, null, null, null, false,
  79:           null, null, null, null);
  80:   }
  81: 
  82:   /**
  83:    * Determines if the PNG ImageReader can decode the specified input.
  84:    *
  85:    * @param source the source to decode
  86:    */
  87:   public boolean canDecodeInput(Object source) throws IOException
  88:   {
  89:     boolean canDecode = false;
  90:     if (source instanceof ImageInputStream)
  91:       {
  92:         ImageInputStream in = (ImageInputStream) source;
  93:         in.mark();
  94:         canDecode = true;
  95:         for (int i = 0; i < SIGNATURE.length && canDecode; i++)
  96:           {
  97:             byte sig = (byte) in.read();
  98:             if (sig != SIGNATURE[i]) {
  99:               canDecode = false;
 100:             }
 101:           }
 102:         in.reset();
 103:       }
 104:     return canDecode;
 105:   }
 106: 
 107:   /**
 108:    * Returns a new PNGImageReader instance.
 109:    *
 110:    * @param extension the extension, ignored
 111:    */
 112:   public ImageReader createReaderInstance(Object extension)
 113:     throws IOException
 114:   {
 115:     return new PNGImageReader(this);
 116:   }
 117: 
 118:   /**
 119:    * Returns a description.
 120:    *
 121:    * @param locale the locale
 122:    */
 123:   public String getDescription(Locale locale)
 124:   {
 125:     return "Portable Network Graphics";
 126:   }
 127: 
 128: }