1 /* JPEGQTable.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 gnu.java.lang.CPStringBuilder; 42 43 /** 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 48 * zig-zag order. 49 */ 50 public class JPEGQTable 51 { 52 /** 53 * The table entries, stored in natural order. 54 */ 55 private int[] table; 56 57 /** 58 * The standard JPEG luminance quantization table. Values are 59 * stored in natural order. 60 */ 61 public static final JPEGQTable K1Luminance = new JPEGQTable(new int[] 62 { 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 71 }, false); 72 73 /** 74 * The standard JPEG luminance quantization table, scaled by 75 * one-half. Values are stored in natural order. 76 */ 77 public static final JPEGQTable K1Div2Luminance = 78 K1Luminance.getScaledInstance(0.5f, true); 79 80 /** 81 * The standard JPEG chrominance quantization table. Values are 82 * stored in natural order. 83 */ 84 public static final JPEGQTable K2Chrominance = new JPEGQTable(new int[] 85 { 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 94 }, false); 95 96 /** 97 * The standard JPEG chrominance quantization table, scaled by 98 * one-half. Values are stored in natural order. 99 */ 100 public static final JPEGQTable K2Div2Chrominance = 101 K2Chrominance.getScaledInstance(0.5f, true); 102 103 /** 104 * Construct a new JPEG quantization table. A copy is created of 105 * the table argument. 106 * 107 * @param table the 64-element value table, stored in natural order 108 * 109 * @throws IllegalArgumentException if the table is null or if 110 * table's length is not equal to 64. 111 */ JPEGQTable(int[] table)112 public JPEGQTable(int[] table) 113 { 114 this(checkTable(table), true); 115 } 116 117 /** 118 * Private constructor that avoids unnecessary copying and argument 119 * checking. 120 * 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 123 */ JPEGQTable(int[] table, boolean copy)124 private JPEGQTable(int[] table, boolean copy) 125 { 126 this.table = copy ? (int[]) table.clone() : table; 127 } 128 checkTable(int[] table)129 private static int[] checkTable(int[] table) 130 { 131 if (table == null || table.length != 64) 132 throw new IllegalArgumentException("invalid JPEG quantization table"); 133 134 return table; 135 } 136 137 /** 138 * Retrieve a copy of the quantization values for this table. 139 * 140 * @return a copy of the quantization value array 141 */ getTable()142 public int[] getTable() 143 { 144 return (int[]) table.clone(); 145 } 146 147 /** 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. 151 * 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 155 * 156 * @return a new scaled JPEG quantization table 157 */ getScaledInstance(float scaleFactor, boolean forceBaseline)158 public JPEGQTable getScaledInstance(float scaleFactor, 159 boolean forceBaseline) 160 { 161 int[] scaledTable = getTable(); 162 int max = forceBaseline ? 255 : 32767; 163 164 for (int i = 0; i < scaledTable.length; i++) 165 { 166 scaledTable[i] = Math.round (scaleFactor * (float) scaledTable[i]); 167 if (scaledTable[i] < 1) 168 scaledTable[i] = 1; 169 else if (scaledTable[i] > max) 170 scaledTable[i] = max; 171 } 172 173 // Do not copy scaledTable. It is already a copy because we used 174 // getTable to retrieve it. 175 return new JPEGQTable(scaledTable, false); 176 } 177 178 /** 179 * Create a string representing this JPEG quantization table. 180 */ toString()181 public String toString() 182 { 183 CPStringBuilder buffer = new CPStringBuilder(); 184 185 buffer.append("JPEGQTable:\n"); 186 for (int i = 0; i < 8; i++) 187 { 188 buffer.append(" "); 189 for (int j = 0; j < 8; j++) 190 { 191 buffer.append(table[i * 8 + j] + " "); 192 } 193 buffer.append("\n"); 194 } 195 196 return buffer.toString(); 197 } 198 } 199