/* |
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* Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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package javax.imageio.plugins.jpeg; |
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import java.util.Arrays; |
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/** |
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* A class encapsulating a single JPEG quantization table. |
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* The elements appear in natural order (as opposed to zig-zag order). |
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* Static variables are provided for the "standard" tables taken from |
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* Annex K of the JPEG specification, as well as the default tables |
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* conventionally used for visually lossless encoding. |
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* <p> |
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* For more information about the operation of the standard JPEG plug-in, |
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* see the <A HREF="../../metadata/doc-files/jpeg_metadata.html">JPEG |
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* metadata format specification and usage notes</A> |
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*/ |
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public class JPEGQTable { |
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private static final int[] k1 = { |
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16, 11, 10, 16, 24, 40, 51, 61, |
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12, 12, 14, 19, 26, 58, 60, 55, |
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14, 13, 16, 24, 40, 57, 69, 56, |
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14, 17, 22, 29, 51, 87, 80, 62, |
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18, 22, 37, 56, 68, 109, 103, 77, |
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24, 35, 55, 64, 81, 104, 113, 92, |
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49, 64, 78, 87, 103, 121, 120, 101, |
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72, 92, 95, 98, 112, 100, 103, 99, |
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}; |
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private static final int[] k1div2 = { |
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8, 6, 5, 8, 12, 20, 26, 31, |
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6, 6, 7, 10, 13, 29, 30, 28, |
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7, 7, 8, 12, 20, 29, 35, 28, |
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7, 9, 11, 15, 26, 44, 40, 31, |
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9, 11, 19, 28, 34, 55, 52, 39, |
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12, 18, 28, 32, 41, 52, 57, 46, |
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25, 32, 39, 44, 52, 61, 60, 51, |
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36, 46, 48, 49, 56, 50, 52, 50, |
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}; |
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private static final int[] k2 = { |
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17, 18, 24, 47, 99, 99, 99, 99, |
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18, 21, 26, 66, 99, 99, 99, 99, |
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24, 26, 56, 99, 99, 99, 99, 99, |
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47, 66, 99, 99, 99, 99, 99, 99, |
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99, 99, 99, 99, 99, 99, 99, 99, |
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99, 99, 99, 99, 99, 99, 99, 99, |
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99, 99, 99, 99, 99, 99, 99, 99, |
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99, 99, 99, 99, 99, 99, 99, 99, |
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}; |
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private static final int[] k2div2 = { |
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9, 9, 12, 24, 50, 50, 50, 50, |
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9, 11, 13, 33, 50, 50, 50, 50, |
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12, 13, 28, 50, 50, 50, 50, 50, |
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24, 33, 50, 50, 50, 50, 50, 50, |
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50, 50, 50, 50, 50, 50, 50, 50, |
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50, 50, 50, 50, 50, 50, 50, 50, |
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50, 50, 50, 50, 50, 50, 50, 50, |
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50, 50, 50, 50, 50, 50, 50, 50, |
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}; |
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/** |
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* The sample luminance quantization table given in the JPEG |
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* specification, table K.1. According to the specification, |
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* these values produce "good" quality output. |
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* @see #K1Div2Luminance |
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*/ |
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public static final JPEGQTable |
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K1Luminance = new JPEGQTable(k1, false); |
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/** |
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* The sample luminance quantization table given in the JPEG |
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* specification, table K.1, with all elements divided by 2. |
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* According to the specification, these values produce "very good" |
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* quality output. This is the table usually used for "visually lossless" |
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* encoding, and is the default luminance table used if the default |
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* tables and quality settings are used. |
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* @see #K1Luminance |
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*/ |
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public static final JPEGQTable |
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K1Div2Luminance = new JPEGQTable(k1div2, false); |
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/** |
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* The sample chrominance quantization table given in the JPEG |
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* specification, table K.2. According to the specification, |
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* these values produce "good" quality output. |
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* @see #K2Div2Chrominance |
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*/ |
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public static final JPEGQTable K2Chrominance = |
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new JPEGQTable(k2, false); |
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/** |
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* The sample chrominance quantization table given in the JPEG |
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* specification, table K.1, with all elements divided by 2. |
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* According to the specification, these values produce "very good" |
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* quality output. This is the table usually used for "visually lossless" |
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* encoding, and is the default chrominance table used if the default |
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* tables and quality settings are used. |
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* @see #K2Chrominance |
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*/ |
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public static final JPEGQTable K2Div2Chrominance = |
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new JPEGQTable(k2div2, false); |
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private int[] qTable; |
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private JPEGQTable(int[] table, boolean copy) { |
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qTable = (copy) ? Arrays.copyOf(table, table.length) : table; |
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} |
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/** |
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* Constructs a quantization table from the argument, which must |
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* contain 64 elements in natural order (not zig-zag order). |
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* A copy is made of the the input array. |
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* @param table the quantization table, as an <code>int</code> array. |
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* @throws IllegalArgumentException if <code>table</code> is |
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* <code>null</code> or <code>table.length</code> is not equal to 64. |
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*/ |
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public JPEGQTable(int[] table) { |
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if (table == null) { |
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throw new IllegalArgumentException("table must not be null."); |
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} |
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if (table.length != 64) { |
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throw new IllegalArgumentException("table.length != 64"); |
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} |
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qTable = Arrays.copyOf(table, table.length); |
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} |
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/** |
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* Returns a copy of the current quantization table as an array |
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* of {@code int}s in natural (not zig-zag) order. |
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* @return A copy of the current quantization table. |
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*/ |
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public int[] getTable() { |
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return Arrays.copyOf(qTable, qTable.length); |
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} |
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/** |
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* Returns a new quantization table where the values are multiplied |
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* by <code>scaleFactor</code> and then clamped to the range 1..32767 |
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* (or to 1..255 if <code>forceBaseline</code> is true). |
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* <p> |
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* Values of <code>scaleFactor</code> less than 1 tend to improve |
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* the quality level of the table, and values greater than 1.0 |
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* degrade the quality level of the table. |
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* @param scaleFactor multiplication factor for the table. |
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* @param forceBaseline if <code>true</code>, |
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* the values will be clamped to the range 1..255 |
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* @return a new quantization table that is a linear multiple |
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* of the current table. |
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*/ |
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public JPEGQTable getScaledInstance(float scaleFactor, |
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boolean forceBaseline) { |
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int max = (forceBaseline) ? 255 : 32767; |
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int[] scaledTable = new int[qTable.length]; |
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for (int i=0; i<qTable.length; i++) { |
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int sv = (int)((qTable[i] * scaleFactor)+0.5f); |
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if (sv < 1) { |
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sv = 1; |
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} |
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if (sv > max) { |
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sv = max; |
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} |
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scaledTable[i] = sv; |
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} |
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return new JPEGQTable(scaledTable); |
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} |
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/** |
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* Returns a {@code String} representing this quantization table. |
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* @return a {@code String} representing this quantization table. |
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*/ |
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public String toString() { |
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String ls = System.getProperty("line.separator", "\n"); |
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StringBuilder sb = new StringBuilder("JPEGQTable:"+ls); |
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for (int i=0; i < qTable.length; i++) { |
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if (i % 8 == 0) { |
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sb.append('\t'); |
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} |
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sb.append(qTable[i]); |
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sb.append(((i % 8) == 7) ? ls : ' '); |
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} |
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return sb.toString(); |
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} |
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} |