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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: */ 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: */ 124: private JPEGQTable(int[] table, boolean copy) 125: { 126: this.table = copy ? (int[]) table.clone() : table; 127: } 128: 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: */ 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: */ 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: */ 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: }