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Diffstat (limited to 'libjava/classpath/javax/imageio/plugins/jpeg/JPEGQTable.java')
| -rw-r--r-- | libjava/classpath/javax/imageio/plugins/jpeg/JPEGQTable.java | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/libjava/classpath/javax/imageio/plugins/jpeg/JPEGQTable.java b/libjava/classpath/javax/imageio/plugins/jpeg/JPEGQTable.java new file mode 100644 index 000000000..259d0aa64 --- /dev/null +++ b/libjava/classpath/javax/imageio/plugins/jpeg/JPEGQTable.java @@ -0,0 +1,198 @@ +/* JPEGQTable.java -- + Copyright (C) 2006 Free Software Foundation, Inc. + + This file is part of GNU Classpath. + + GNU Classpath is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2, or (at your option) + any later version. + + GNU Classpath is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + General Public License for more details. + + You should have received a copy of the GNU General Public License + along with GNU Classpath; see the file COPYING. If not, write to the + Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + 02110-1301 USA. + + Linking this library statically or dynamically with other modules is + making a combined work based on this library. Thus, the terms and + conditions of the GNU General Public License cover the whole + combination. + + As a special exception, the copyright holders of this library give you + permission to link this library with independent modules to produce an + executable, regardless of the license terms of these independent + modules, and to copy and distribute the resulting executable under + terms of your choice, provided that you also meet, for each linked + independent module, the terms and conditions of the license of that + module. An independent module is a module which is not derived from + or based on this library. If you modify this library, you may extend + this exception to your version of the library, but you are not + obligated to do so. If you do not wish to do so, delete this + exception statement from your version. */ + + +package javax.imageio.plugins.jpeg; + +import gnu.java.lang.CPStringBuilder; + +/** + * The JPEGQTable class represents a quantization table that can be + * used to encode or decode a JPEG stream. The standard JPEG + * luminance and chrominance quantization tables are provided as + * static fields. Table entries are stored in natural order, not + * zig-zag order. + */ +public class JPEGQTable +{ + /** + * The table entries, stored in natural order. + */ + private int[] table; + + /** + * The standard JPEG luminance quantization table. Values are + * stored in natural order. + */ + public static final JPEGQTable K1Luminance = new JPEGQTable(new int[] + { + 16, 11, 10, 16, 24, 40, 51, 61, + 12, 12, 14, 19, 26, 58, 60, 55, + 14, 13, 16, 24, 40, 57, 69, 56, + 14, 17, 22, 29, 51, 87, 80, 62, + 18, 22, 37, 56, 68, 109, 103, 77, + 24, 35, 55, 64, 81, 104, 113, 92, + 49, 64, 78, 87, 103, 121, 120, 101, + 72, 92, 95, 98, 112, 100, 103, 99 + }, false); + + /** + * The standard JPEG luminance quantization table, scaled by + * one-half. Values are stored in natural order. + */ + public static final JPEGQTable K1Div2Luminance = + K1Luminance.getScaledInstance(0.5f, true); + + /** + * The standard JPEG chrominance quantization table. Values are + * stored in natural order. + */ + public static final JPEGQTable K2Chrominance = new JPEGQTable(new int[] + { + 17, 18, 24, 47, 99, 99, 99, 99, + 18, 21, 26, 66, 99, 99, 99, 99, + 24, 26, 56, 99, 99, 99, 99, 99, + 47, 66, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99 + }, false); + + /** + * The standard JPEG chrominance quantization table, scaled by + * one-half. Values are stored in natural order. + */ + public static final JPEGQTable K2Div2Chrominance = + K2Chrominance.getScaledInstance(0.5f, true); + + /** + * Construct a new JPEG quantization table. A copy is created of + * the table argument. + * + * @param table the 64-element value table, stored in natural order + * + * @throws IllegalArgumentException if the table is null or if + * table's length is not equal to 64. + */ + public JPEGQTable(int[] table) + { + this(checkTable(table), true); + } + + /** + * Private constructor that avoids unnecessary copying and argument + * checking. + * + * @param table the 64-element value table, stored in natural order + * @param copy true if a copy should be created of the given table + */ + private JPEGQTable(int[] table, boolean copy) + { + this.table = copy ? (int[]) table.clone() : table; + } + + private static int[] checkTable(int[] table) + { + if (table == null || table.length != 64) + throw new IllegalArgumentException("invalid JPEG quantization table"); + + return table; + } + + /** + * Retrieve a copy of the quantization values for this table. + * + * @return a copy of the quantization value array + */ + public int[] getTable() + { + return (int[]) table.clone(); + } + + /** + * Retrieve a copy of this JPEG quantization table with every value + * scaled by the given scale factor, and clamped from 1 to 255 + * baseline or from 1 to 32767 otherwise. + * + * @param scaleFactor the factor by which to scale this table + * @param forceBaseline clamp scaled values to a maximum of 255 if + * true, 32767 if false + * + * @return a new scaled JPEG quantization table + */ + public JPEGQTable getScaledInstance(float scaleFactor, + boolean forceBaseline) + { + int[] scaledTable = getTable(); + int max = forceBaseline ? 255 : 32767; + + for (int i = 0; i < scaledTable.length; i++) + { + scaledTable[i] = Math.round (scaleFactor * (float) scaledTable[i]); + if (scaledTable[i] < 1) + scaledTable[i] = 1; + else if (scaledTable[i] > max) + scaledTable[i] = max; + } + + // Do not copy scaledTable. It is already a copy because we used + // getTable to retrieve it. + return new JPEGQTable(scaledTable, false); + } + + /** + * Create a string representing this JPEG quantization table. + */ + public String toString() + { + CPStringBuilder buffer = new CPStringBuilder(); + + buffer.append("JPEGQTable:\n"); + for (int i = 0; i < 8; i++) + { + buffer.append(" "); + for (int j = 0; j < 8; j++) + { + buffer.append(table[i * 8 + j] + " "); + } + buffer.append("\n"); + } + + return buffer.toString(); + } +} |