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152 lines
6.1 KiB
152 lines
6.1 KiB
/*
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*
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* Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*/
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/**********************************************************************
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**********************************************************************
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**********************************************************************
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*** COPYRIGHT (c) 1997-1998 Eastman Kodak Company. ***
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*** As an unpublished work pursuant to Title 17 of the United ***
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*** States Code. All rights reserved. ***
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**********************************************************************
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**********************************************************************
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**********************************************************************/
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package com.sun.image.codec.jpeg;
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/** Class to encapsulate the JPEG quantization tables.
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* <p>
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* Note that the classes in the com.sun.image.codec.jpeg package are not
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* part of the core Java APIs. They are a part of Sun's JDK and JRE
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* distributions. Although other licensees may choose to distribute these
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* classes, developers cannot depend on their availability in non-Sun
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* implementations. We expect that equivalent functionality will eventually
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* be available in a core API or standard extension.
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* <p>
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*/
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public class JPEGQTable {
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/** Quantization step for each coefficient in zig-zag order */
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private int quantval[];
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/** The number of coefficients in a DCT block */
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private static final byte QTABLESIZE = 64;
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/**
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* This is the sample luminance quantization table given in the
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* JPEG spec section K.1, expressed in zigzag order. The spec says
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* that the values given produce "good" quality, and when divided
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* by 2, "very good" quality.
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*/
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public static final JPEGQTable StdLuminance = new JPEGQTable();
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static {
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int [] lumVals = {
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16, 11, 12, 14, 12, 10, 16, 14,
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13, 14, 18, 17, 16, 19, 24, 40,
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26, 24, 22, 22, 24, 49, 35, 37,
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29, 40, 58, 51, 61, 60, 57, 51,
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56, 55, 64, 72, 92, 78, 64, 68,
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87, 69, 55, 56, 80, 109, 81, 87,
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95, 98, 103, 104, 103, 62, 77, 113,
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121, 112, 100, 120, 92, 101, 103, 99
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};
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StdLuminance.quantval = lumVals;
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}
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/**
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* This is the sample luminance quantization table given in the
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* JPEG spec section K.1, expressed in zigzag order. The spec says
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* that the values given produce "good" quality, and when divided
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* by 2, "very good" quality.
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*/
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public static final JPEGQTable StdChrominance = new JPEGQTable();
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static {
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int [] chromVals = {
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17, 18, 18, 24, 21, 24, 47, 26,
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26, 47, 99, 66, 56, 66, 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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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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StdChrominance.quantval = chromVals;
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}
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/**
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* Constructs an empty quantization table. This is used to create
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* the Std Q-Tables.
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*/
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private JPEGQTable() {
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quantval = new int[QTABLESIZE];
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}
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/**
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* Constructs an quantization table from the array that was
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* passed. The coefficents must be in zig-zag order. The array
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* must be of length 64.
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* @param table the quantization table (this is copied).
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*/
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public JPEGQTable( int table[] ) {
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if ( table.length != QTABLESIZE ) {
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throw new IllegalArgumentException
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("Quantization table is the wrong size.");
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} else {
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quantval = new int[QTABLESIZE];
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System.arraycopy( table, 0, quantval, 0, QTABLESIZE );
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}
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}
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/**
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* Returns the current quantization table as an array of ints in
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* zig zag order.
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* @return A copy of the contained quantization table.
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*/
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public int[] getTable() {
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int[] table = new int[QTABLESIZE];
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System.arraycopy( quantval, 0, table, 0, QTABLESIZE );
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return table;
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}
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/**
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* Returns a new Quantization table where the values are
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* multiplied by scaleFactor and then clamped to the range
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* 1..32767 (or to 1..255 if forceBaseline is 'true'). <P>
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* Values less than one tend to improve the quality level of the
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* table, and values greater than one degrade the quality level of
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* the table.
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* @param scaleFactor the multiplication factor for the table
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* @param forceBaseline if true the values will be clamped
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* to the range [1 .. 255]
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* @return A new Q-Table that is a linear multiple of this Q-Table
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*/
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public JPEGQTable getScaledInstance(float scaleFactor,
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boolean forceBaseline ) {
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long max = (forceBaseline)?255L:32767L;
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int []ret = new int[QTABLESIZE];
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for (int i=0; i<QTABLESIZE; i++ ) {
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long holder = (long)((quantval[i] * scaleFactor) + 0.5);
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// limit to valid range
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if (holder <= 0L) holder = 1L;
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// Max quantizer for 12 bits
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if (holder > max ) holder = max;
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ret[i] = (int)holder;
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}
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return new JPEGQTable(ret);
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}
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}
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