001    /* JPEGImageReadParam.java --
002     Copyright (C)  2006  Free Software Foundation, Inc.
003    
004     This file is part of GNU Classpath.
005    
006     GNU Classpath is free software; you can redistribute it and/or modify
007     it under the terms of the GNU General Public License as published by
008     the Free Software Foundation; either version 2, or (at your option)
009     any later version.
010    
011     GNU Classpath is distributed in the hope that it will be useful, but
012     WITHOUT ANY WARRANTY; without even the implied warranty of
013     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014     General Public License for more details.
015    
016     You should have received a copy of the GNU General Public License
017     along with GNU Classpath; see the file COPYING.  If not, write to the
018     Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019     02110-1301 USA.
020    
021     Linking this library statically or dynamically with other modules is
022     making a combined work based on this library.  Thus, the terms and
023     conditions of the GNU General Public License cover the whole
024     combination.
025    
026     As a special exception, the copyright holders of this library give you
027     permission to link this library with independent modules to produce an
028     executable, regardless of the license terms of these independent
029     modules, and to copy and distribute the resulting executable under
030     terms of your choice, provided that you also meet, for each linked
031     independent module, the terms and conditions of the license of that
032     module.  An independent module is a module which is not derived from
033     or based on this library.  If you modify this library, you may extend
034     this exception to your version of the library, but you are not
035     obligated to do so.  If you do not wish to do so, delete this
036     exception statement from your version. */
037    
038    
039    package javax.imageio.plugins.jpeg;
040    
041    import javax.imageio.ImageReadParam;
042    
043    /**
044     * The JPEGImageReadParam class is only used to set JPEG decoding
045     * tables for streams that do not provide their own tables.  If a
046     * stream does not provide tables and a custom JPEGImageReadParam is
047     * not provided, then the standard JPEG tables are used from the
048     * JPEGQTable and JPEGHuffmanTable classes.  If a stream does provide
049     * decoding tables then JPEGImageReadParam will be ignored.
050     * JPEGImageReadParam cannot be used to retrieve the tables from a
051     * stream.  Instead, use IIOMetadata for this purpose.
052     *
053     * A JPEGImageReadParam instance is retrieved from the built-in JPEG
054     * ImageReader using the getDefaultImageReadParam method.
055     */
056    public class JPEGImageReadParam
057      extends ImageReadParam
058    {
059      private JPEGQTable[] qTables;
060      private JPEGHuffmanTable[] DCHuffmanTables;
061      private JPEGHuffmanTable[] ACHuffmanTables;
062    
063      /**
064       * Construct a JPEGImageReadParam.
065       */
066      public JPEGImageReadParam()
067      {
068        super();
069      }
070    
071      /**
072       * Check if the decoding tables are set.
073       *
074       * @return true if the decoding tables are set, false otherwise
075       */
076      public boolean areTablesSet()
077      {
078        // If qTables is not null then all tables are set.
079        return (qTables != null);
080      }
081    
082      /**
083       * Set the quantization and Huffman tables that will be used to
084       * decode the stream.  Copies are created of the array arguments.
085       * The number of Huffman tables must be the same in both Huffman
086       * table arrays.  No argument may be null and no array may be longer
087       * than four elements.
088       *
089       * @param qTables JPEG quantization tables
090       * @param DCHuffmanTables JPEG DC Huffman tables
091       * @param ACHuffmanTables JPEG AC Huffman tables
092       *
093       * @throws IllegalArgumentException if any argument is null, if any
094       * of the arrays are longer than four elements, or if the Huffman
095       * table arrays do not have the same number of elements
096       */
097      public void setDecodeTables(JPEGQTable[] qTables,
098                                  JPEGHuffmanTable[] DCHuffmanTables,
099                                  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    }