API Overview API Index Package Overview Direct link to this page
JDK 1.6
  javax.imageio.plugins.jpeg. JPEGImageReadParam View Javadoc
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182

/*
 * @(#)JPEGImageReadParam.java	1.12 05/11/17
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.imageio.plugins.jpeg;

import javax.imageio.ImageReadParam;

/**
 * This class adds the ability to set JPEG quantization and Huffman
 * tables when using the built-in JPEG reader plug-in.  An instance of
 * this class will be returned from the
 * <code>getDefaultImageReadParam</code> methods of the built-in JPEG
 * <code>ImageReader</code>.
 *
 * <p> The sole purpose of these additions is to allow the
 * specification of tables for use in decoding abbreviated streams.
 * The built-in JPEG reader will also accept an ordinary
 * <code>ImageReadParam</code>, which is sufficient for decoding
 * non-abbreviated streams.
 *
 * <p> While tables for abbreviated streams are often obtained by
 * first reading another abbreviated stream containing only the
 * tables, in some applications the tables are fixed ahead of time.
 * This class allows the tables to be specified directly from client
 * code.  If no tables are specified either in the stream or in a
 * <code>JPEGImageReadParam</code>, then the stream is presumed to use
 * the "standard" visually lossless tables.  See {@link JPEGQTable
 * <code>JPEGQTable</code>} and {@link JPEGHuffmanTable
 * <code>JPEGHuffmanTable</code>} for more information on the default
 * tables.
 *
 * <p> The default <code>JPEGImageReadParam</code> returned by the
 * <code>getDefaultReadParam</code> method of the builtin JPEG reader
 * contains no tables.  Default tables may be obtained from the table
 * classes {@link JPEGQTable <code>JPEGQTable</code>} and {@link
 * JPEGHuffmanTable <code>JPEGHuffmanTable</code>}.
 *
 * <p> If a stream does contain tables, the tables given in a
 * <code>JPEGImageReadParam</code> are ignored.  Furthermore, if the
 * first image in a stream does contain tables and subsequent ones do
 * not, then the tables given in the first image are used for all the
 * abbreviated images.  Once tables have been read from a stream, they
 * can be overridden only by tables subsequently read from the same
 * stream.  In order to specify new tables, the {@link
 * javax.imageio.ImageReader#setInput <code>setInput</code>} method of
 * the reader must be called to change the stream.
 *
 * <p> Note that this class does not provide a means for obtaining the
 * tables found in a stream.  These may be extracted from a stream by
 * consulting the <code>IIOMetadata</code> object returned by the
 * reader.
 *
 * <p>
 * For more information about the operation of the built-in JPEG plug-ins,
 * see the <A HREF="../../metadata/doc-files/jpeg_metadata.html">JPEG
 * metadata format specification and usage notes</A>.
 *
 * @version 0.5
 */
public class JPEGImageReadParam extends ImageReadParam {

    private JPEGQTable[] qTables = null;
    private JPEGHuffmanTable[] DCHuffmanTables = null;
    private JPEGHuffmanTable[] ACHuffmanTables = null;

    /**
     * Constructs a <code>JPEGImageReadParam</code>.
     */
    public JPEGImageReadParam() {
        super();
    }
    
    /**
     * Returns <code>true</code> if tables are currently set.
     *
     * @return <code>true</code> if tables are present.
     */
    public boolean areTablesSet() {
        return (qTables != null);
    }

    /**
     * Sets the quantization and Huffman tables to use in decoding
     * abbreviated streams.  There may be a maximum of 4 tables of
     * each type.  These tables are ignored once tables are
     * encountered in the stream.  All arguments must be
     * non-<code>null</code>.  The two arrays of Huffman tables must
     * have the same number of elements.  The table specifiers in the
     * frame and scan headers in the stream are assumed to be
     * equivalent to indices into these arrays.  The argument arrays
     * are copied by this method.
     *
     * @param qTables an array of quantization table objects.
     * @param DCHuffmanTables an array of Huffman table objects.
     * @param ACHuffmanTables an array of Huffman table objects.
     *
     * @exception IllegalArgumentException if any of the arguments
     * is <code>null</code>, has more than 4 elements, or if the
     * numbers of DC and AC tables differ.
     *
     * @see #unsetDecodeTables
     */
    public void setDecodeTables(JPEGQTable[] qTables, 
                                JPEGHuffmanTable[] DCHuffmanTables,
                                JPEGHuffmanTable[] ACHuffmanTables) {
        if ((qTables == null) ||
            (DCHuffmanTables == null) ||
            (ACHuffmanTables == null) ||
            (qTables.length > 4) ||
            (DCHuffmanTables.length > 4) ||
            (ACHuffmanTables.length > 4) ||
            (DCHuffmanTables.length != ACHuffmanTables.length)) {
                throw new IllegalArgumentException
                    ("Invalid JPEG table arrays");
        }
        this.qTables = (JPEGQTable[])qTables.clone();
        this.DCHuffmanTables = (JPEGHuffmanTable[])DCHuffmanTables.clone();
        this.ACHuffmanTables = (JPEGHuffmanTable[])ACHuffmanTables.clone();
    }

    /**
     * Removes any quantization and Huffman tables that are currently
     * set.
     *
     * @see #setDecodeTables
     */
    public void unsetDecodeTables() {
        this.qTables = null;
        this.DCHuffmanTables = null;
        this.ACHuffmanTables = null;
    }

    /**
     * Returns a copy of the array of quantization tables set on the
     * most recent call to <code>setDecodeTables</code>, or
     * <code>null</code> if tables are not currently set.
     *
     * @return an array of <code>JPEGQTable</code> objects, or
     * <code>null</code>.
     *
     * @see #setDecodeTables
     */
    public JPEGQTable[] getQTables() {
        return (qTables != null) ? (JPEGQTable[])qTables.clone() : null;
    }
    
    /**
     * Returns a copy of the array of DC Huffman tables set on the
     * most recent call to <code>setDecodeTables</code>, or
     * <code>null</code> if tables are not currently set.
     *
     * @return an array of <code>JPEGHuffmanTable</code> objects, or
     * <code>null</code>.
     *
     * @see #setDecodeTables
     */
    public JPEGHuffmanTable[] getDCHuffmanTables() {
        return (DCHuffmanTables != null)
            ? (JPEGHuffmanTable[])DCHuffmanTables.clone() 
            : null;
    }

    /**
     * Returns a copy of the array of AC Huffman tables set on the
     * most recent call to <code>setDecodeTables</code>, or
     * <code>null</code> if tables are not currently set.
     *
     * @return an array of <code>JPEGHuffmanTable</code> objects, or
     * <code>null</code>.
     *
     * @see #setDecodeTables
     */
    public JPEGHuffmanTable[] getACHuffmanTables() {
        return (ACHuffmanTables != null) 
            ? (JPEGHuffmanTable[])ACHuffmanTables.clone() 
            : null;
    }
}

Generated By: JavaOnTracks Doclet 0.1.4     ©Thibaut Colar