2 Copyright (C) 2006 Free Software Foundation, Inc.
4 This file is part of GNU Classpath.
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)
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.
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
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
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. */
39 package javax.imageio.plugins.jpeg;
41 import gnu.java.lang.CPStringBuilder;
44 * The JPEGQTable class represents a quantization table that can be
45 * used to encode or decode a JPEG stream. The standard JPEG
46 * luminance and chrominance quantization tables are provided as
47 * static fields. Table entries are stored in natural order, not
50 public class JPEGQTable
53 * The table entries, stored in natural order.
58 * The standard JPEG luminance quantization table. Values are
59 * stored in natural order.
61 public static final JPEGQTable K1Luminance = new JPEGQTable(new int[]
63 16, 11, 10, 16, 24, 40, 51, 61,
64 12, 12, 14, 19, 26, 58, 60, 55,
65 14, 13, 16, 24, 40, 57, 69, 56,
66 14, 17, 22, 29, 51, 87, 80, 62,
67 18, 22, 37, 56, 68, 109, 103, 77,
68 24, 35, 55, 64, 81, 104, 113, 92,
69 49, 64, 78, 87, 103, 121, 120, 101,
70 72, 92, 95, 98, 112, 100, 103, 99
74 * The standard JPEG luminance quantization table, scaled by
75 * one-half. Values are stored in natural order.
77 public static final JPEGQTable K1Div2Luminance =
78 K1Luminance.getScaledInstance(0.5f, true);
81 * The standard JPEG chrominance quantization table. Values are
82 * stored in natural order.
84 public static final JPEGQTable K2Chrominance = new JPEGQTable(new int[]
86 17, 18, 24, 47, 99, 99, 99, 99,
87 18, 21, 26, 66, 99, 99, 99, 99,
88 24, 26, 56, 99, 99, 99, 99, 99,
89 47, 66, 99, 99, 99, 99, 99, 99,
90 99, 99, 99, 99, 99, 99, 99, 99,
91 99, 99, 99, 99, 99, 99, 99, 99,
92 99, 99, 99, 99, 99, 99, 99, 99,
93 99, 99, 99, 99, 99, 99, 99, 99
97 * The standard JPEG chrominance quantization table, scaled by
98 * one-half. Values are stored in natural order.
100 public static final JPEGQTable K2Div2Chrominance =
101 K2Chrominance.getScaledInstance(0.5f, true);
104 * Construct a new JPEG quantization table. A copy is created of
105 * the table argument.
107 * @param table the 64-element value table, stored in natural order
109 * @throws IllegalArgumentException if the table is null or if
110 * table's length is not equal to 64.
112 public JPEGQTable(int[] table)
114 this(checkTable(table), true);
118 * Private constructor that avoids unnecessary copying and argument
121 * @param table the 64-element value table, stored in natural order
122 * @param copy true if a copy should be created of the given table
124 private JPEGQTable(int[] table, boolean copy)
126 this.table = copy ? (int[]) table.clone() : table;
129 private static int[] checkTable(int[] table)
131 if (table == null || table.length != 64)
132 throw new IllegalArgumentException("invalid JPEG quantization table");
138 * Retrieve a copy of the quantization values for this table.
140 * @return a copy of the quantization value array
142 public int[] getTable()
144 return (int[]) table.clone();
148 * Retrieve a copy of this JPEG quantization table with every value
149 * scaled by the given scale factor, and clamped from 1 to 255
150 * baseline or from 1 to 32767 otherwise.
152 * @param scaleFactor the factor by which to scale this table
153 * @param forceBaseline clamp scaled values to a maximum of 255 if
154 * true, 32767 if false
156 * @return a new scaled JPEG quantization table
158 public JPEGQTable getScaledInstance(float scaleFactor,
159 boolean forceBaseline)
161 int[] scaledTable = getTable();
162 int max = forceBaseline ? 255 : 32767;
164 for (int i = 0; i < scaledTable.length; i++)
166 scaledTable[i] = Math.round (scaleFactor * (float) scaledTable[i]);
167 if (scaledTable[i] < 1)
169 else if (scaledTable[i] > max)
170 scaledTable[i] = max;
173 // Do not copy scaledTable. It is already a copy because we used
174 // getTable to retrieve it.
175 return new JPEGQTable(scaledTable, false);
179 * Create a string representing this JPEG quantization table.
181 public String toString()
183 CPStringBuilder buffer = new CPStringBuilder();
185 buffer.append("JPEGQTable:\n");
186 for (int i = 0; i < 8; i++)
189 for (int j = 0; j < 8; j++)
191 buffer.append(table[i * 8 + j] + " ");
196 return buffer.toString();