libjava/classpath/javax/imageio/plugins/jpeg/JPEGImageReadParam.java

   1 /* JPEGImageReadParam.java --
   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 javax.imageio.plugins.jpeg;
  40
  41 import javax.imageio.ImageReadParam;
  42
  43 /**
  44  * The JPEGImageReadParam class is only used to set JPEG decoding
  45  * tables for streams that do not provide their own tables.  If a
  46  * stream does not provide tables and a custom JPEGImageReadParam is
  47  * not provided, then the standard JPEG tables are used from the
  48  * JPEGQTable and JPEGHuffmanTable classes.  If a stream does provide
  49  * decoding tables then JPEGImageReadParam will be ignored.
  50  * JPEGImageReadParam cannot be used to retrieve the tables from a
  51  * stream.  Instead, use IIOMetadata for this purpose.
  52  *
  53  * A JPEGImageReadParam instance is retrieved from the built-in JPEG
  54  * ImageReader using the getDefaultImageReadParam method.
  55  */
  56 public class JPEGImageReadParam
  57   extends ImageReadParam
  58 {
  59   private JPEGQTable[] qTables;
  60   private JPEGHuffmanTable[] DCHuffmanTables;
  61   private JPEGHuffmanTable[] ACHuffmanTables;
  62
  63   /**
  64    * Construct a JPEGImageReadParam.
  65    */
  66   public JPEGImageReadParam()
  67   {
  68     super();
  69   }
  70
  71   /**
  72    * Check if the decoding tables are set.
  73    *
  74    * @return true if the decoding tables are set, false otherwise
  75    */
  76   public boolean areTablesSet()
  77   {
  78     // If qTables is not null then all tables are set.
  79     return (qTables != null);
  80   }
  81
  82   /**
  83    * Set the quantization and Huffman tables that will be used to
  84    * decode the stream.  Copies are created of the array arguments.
  85    * The number of Huffman tables must be the same in both Huffman
  86    * table arrays.  No argument may be null and no array may be longer
  87    * than four elements.
  88    *
  89    * @param qTables JPEG quantization tables
  90    * @param DCHuffmanTables JPEG DC Huffman tables
  91    * @param ACHuffmanTables JPEG AC Huffman tables
  92    *
  93    * @throws IllegalArgumentException if any argument is null, if any
  94    * of the arrays are longer than four elements, or if the Huffman
  95    * table arrays do not have the same number of elements
  96    */
  97   public void setDecodeTables(JPEGQTable[] qTables,
  98                               JPEGHuffmanTable[] DCHuffmanTables,
  99                               JPEGHuffmanTable[] ACHuffmanTables)
 100   {
 101     if (qTables == null || DCHuffmanTables == null || ACHuffmanTables == null)
 102       throw new IllegalArgumentException("null argument");
 103
 104     if (qTables.length > 4 || DCHuffmanTables.length > 4
 105         || ACHuffmanTables.length > 4)
 106       throw new IllegalArgumentException("argument has too many elements");
 107
 108     if (DCHuffmanTables.length != ACHuffmanTables.length)
 109       throw new IllegalArgumentException("Huffman table arrays differ in length");
 110
 111     // Do a shallow copy.  JPEGQTable's data is not directly
 112     // modifyable since JPEGQTable.getTable returns a copy.  Therefore
 113     // it is safe to have multiple references to a single JPEGQTable.
 114     // Likewise for JPEGHuffmanTable.
 115     this.qTables = (JPEGQTable[]) qTables.clone();
 116     this.DCHuffmanTables = (JPEGHuffmanTable[]) DCHuffmanTables.clone();
 117     this.ACHuffmanTables = (JPEGHuffmanTable[]) ACHuffmanTables.clone();
 118   }
 119
 120   /**
 121    * Clear the quantization and Huffman decoding tables.
 122    */
 123   public void unsetDecodeTables()
 124   {
 125     qTables = null;
 126     DCHuffmanTables = null;
 127     ACHuffmanTables = null;
 128   }
 129
 130   /**
 131    * Retrieve the quantization tables.
 132    *
 133    * @returns an array of JPEG quantization tables
 134    */
 135   public JPEGQTable[] getQTables()
 136   {
 137     return qTables == null ? qTables : (JPEGQTable[]) qTables.clone();
 138   }
 139
 140   /**
 141    * Retrieve the DC Huffman tables.
 142    *
 143    * @return an array of JPEG DC Huffman tables
 144    */
 145   public JPEGHuffmanTable[] getDCHuffmanTables()
 146   {
 147     return DCHuffmanTables == null ? DCHuffmanTables
 148       : (JPEGHuffmanTable[]) DCHuffmanTables.clone();
 149   }
 150
 151   /**
 152    * Retrieve the AC Huffman tables.
 153    *
 154    * @return an array of JPEG AC Huffman tables
 155    */
 156   public JPEGHuffmanTable[] getACHuffmanTables()
 157   {
 158     return ACHuffmanTables == null ? ACHuffmanTables
 159       : (JPEGHuffmanTable[]) ACHuffmanTables.clone();
 160   }
 161 }