1 /*
2 * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.imageio.plugins.jpeg;
27
28 import java.util.Arrays;
29
30 /**
31 * A class encapsulating a single JPEG quantization table.
32 * The elements appear in natural order (as opposed to zig-zag order).
33 * Static variables are provided for the "standard" tables taken from
34 * Annex K of the JPEG specification, as well as the default tables
35 * conventionally used for visually lossless encoding.
36 * <p>
37 * For more information about the operation of the standard JPEG plug-in,
38 * see the <A HREF="../../metadata/doc-files/jpeg_metadata.html">JPEG
39 * metadata format specification and usage notes</A>
40 */
41
42 public class JPEGQTable {
43
44 private static final int[] k1 = {
45 16, 11, 10, 16, 24, 40, 51, 61,
46 12, 12, 14, 19, 26, 58, 60, 55,
47 14, 13, 16, 24, 40, 57, 69, 56,
48 14, 17, 22, 29, 51, 87, 80, 62,
49 18, 22, 37, 56, 68, 109, 103, 77,
50 24, 35, 55, 64, 81, 104, 113, 92,
51 49, 64, 78, 87, 103, 121, 120, 101,
52 72, 92, 95, 98, 112, 100, 103, 99,
53 };
54
55 private static final int[] k1div2 = {
56 8, 6, 5, 8, 12, 20, 26, 31,
57 6, 6, 7, 10, 13, 29, 30, 28,
58 7, 7, 8, 12, 20, 29, 35, 28,
59 7, 9, 11, 15, 26, 44, 40, 31,
60 9, 11, 19, 28, 34, 55, 52, 39,
61 12, 18, 28, 32, 41, 52, 57, 46,
62 25, 32, 39, 44, 52, 61, 60, 51,
63 36, 46, 48, 49, 56, 50, 52, 50,
64 };
65
66 private static final int[] k2 = {
67 17, 18, 24, 47, 99, 99, 99, 99,
68 18, 21, 26, 66, 99, 99, 99, 99,
69 24, 26, 56, 99, 99, 99, 99, 99,
70 47, 66, 99, 99, 99, 99, 99, 99,
71 99, 99, 99, 99, 99, 99, 99, 99,
72 99, 99, 99, 99, 99, 99, 99, 99,
73 99, 99, 99, 99, 99, 99, 99, 99,
74 99, 99, 99, 99, 99, 99, 99, 99,
75 };
76
77 private static final int[] k2div2 = {
78 9, 9, 12, 24, 50, 50, 50, 50,
79 9, 11, 13, 33, 50, 50, 50, 50,
80 12, 13, 28, 50, 50, 50, 50, 50,
81 24, 33, 50, 50, 50, 50, 50, 50,
82 50, 50, 50, 50, 50, 50, 50, 50,
83 50, 50, 50, 50, 50, 50, 50, 50,
84 50, 50, 50, 50, 50, 50, 50, 50,
85 50, 50, 50, 50, 50, 50, 50, 50,
86 };
87
88 /**
89 * The sample luminance quantization table given in the JPEG
90 * specification, table K.1. According to the specification,
91 * these values produce "good" quality output.
92 * @see #K1Div2Luminance
93 */
94 public static final JPEGQTable
95 K1Luminance = new JPEGQTable(k1, false);
96
97 /**
98 * The sample luminance quantization table given in the JPEG
99 * specification, table K.1, with all elements divided by 2.
100 * According to the specification, these values produce "very good"
101 * quality output. This is the table usually used for "visually lossless"
102 * encoding, and is the default luminance table used if the default
103 * tables and quality settings are used.
104 * @see #K1Luminance
105 */
106 public static final JPEGQTable
107 K1Div2Luminance = new JPEGQTable(k1div2, false);
108
109 /**
110 * The sample chrominance quantization table given in the JPEG
111 * specification, table K.2. According to the specification,
112 * these values produce "good" quality output.
113 * @see #K2Div2Chrominance
114 */
115 public static final JPEGQTable K2Chrominance =
116 new JPEGQTable(k2, false);
117
118 /**
119 * The sample chrominance quantization table given in the JPEG
120 * specification, table K.1, with all elements divided by 2.
121 * According to the specification, these values produce "very good"
122 * quality output. This is the table usually used for "visually lossless"
123 * encoding, and is the default chrominance table used if the default
124 * tables and quality settings are used.
125 * @see #K2Chrominance
126 */
127 public static final JPEGQTable K2Div2Chrominance =
128 new JPEGQTable(k2div2, false);
129
130 private int[] qTable;
131
132 private JPEGQTable(int[] table, boolean copy) {
133 qTable = (copy) ? Arrays.copyOf(table, table.length) : table;
134 }
135
136 /**
137 * Constructs a quantization table from the argument, which must
138 * contain 64 elements in natural order (not zig-zag order).
139 * A copy is made of the the input array.
140 * @param table the quantization table, as an <code>int</code> array.
141 * @throws IllegalArgumentException if <code>table</code> is
142 * <code>null</code> or <code>table.length</code> is not equal to 64.
143 */
144 public JPEGQTable(int[] table) {
145 if (table == null) {
146 throw new IllegalArgumentException("table must not be null.");
147 }
148 if (table.length != 64) {
149 throw new IllegalArgumentException("table.length != 64");
150 }
151 qTable = Arrays.copyOf(table, table.length);
152 }
153
154 /**
155 * Returns a copy of the current quantization table as an array
156 * of {@code int}s in natural (not zig-zag) order.
157 * @return A copy of the current quantization table.
158 */
159 public int[] getTable() {
160 return Arrays.copyOf(qTable, qTable.length);
161 }
162
163 /**
164 * Returns a new quantization table where the values are multiplied
165 * by <code>scaleFactor</code> and then clamped to the range 1..32767
166 * (or to 1..255 if <code>forceBaseline</code> is true).
167 * <p>
168 * Values of <code>scaleFactor</code> less than 1 tend to improve
169 * the quality level of the table, and values greater than 1.0
170 * degrade the quality level of the table.
171 * @param scaleFactor multiplication factor for the table.
172 * @param forceBaseline if <code>true</code>,
173 * the values will be clamped to the range 1..255
174 * @return a new quantization table that is a linear multiple
175 * of the current table.
176 */
177 public JPEGQTable getScaledInstance(float scaleFactor,
178 boolean forceBaseline) {
179 int max = (forceBaseline) ? 255 : 32767;
180 int[] scaledTable = new int[qTable.length];
181 for (int i=0; i<qTable.length; i++) {
182 int sv = (int)((qTable[i] * scaleFactor)+0.5f);
183 if (sv < 1) {
184 sv = 1;
185 }
186 if (sv > max) {
187 sv = max;
188 }
189 scaledTable[i] = sv;
190 }
191 return new JPEGQTable(scaledTable);
192 }
193
194 /**
195 * Returns a {@code String} representing this quantization table.
196 * @return a {@code String} representing this quantization table.
197 */
198 public String toString() {
199 String ls = System.getProperty("line.separator", "\n");
200 StringBuilder sb = new StringBuilder();
201 sb.append("JPEGQTable:").append(ls);
202 for (int i=0; i < qTable.length; i++) {
203 if (i % 8 == 0) {
204 sb.append('\t');
205 }
206 sb.append(qTable[i]);
207 sb.append(((i % 8) == 7) ? ls : ' ');
208 }
209 return sb.toString();
210 }
211 }