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211 lines
7.0 KiB
211 lines
7.0 KiB
/*
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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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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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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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}
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