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321 lines
11 KiB
321 lines
11 KiB
/*
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* Copyright (c) 2000, 2013, 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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package javax.imageio.plugins.jpeg;
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import java.util.Locale;
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import javax.imageio.ImageWriteParam;
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import com.sun.imageio.plugins.jpeg.JPEG;
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/**
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* This class adds the ability to set JPEG quantization and Huffman
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* tables when using the built-in JPEG writer plug-in, and to request that
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* optimized Huffman tables be computed for an image. An instance of
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* this class will be returned from the
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* <code>getDefaultImageWriteParam</code> methods of the built-in JPEG
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* <code>ImageWriter</code>.
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* <p> The principal purpose of these additions is to allow the
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* specification of tables to use in encoding abbreviated streams.
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* The built-in JPEG writer will also accept an ordinary
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* <code>ImageWriteParam</code>, in which case the writer will
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* construct the necessary tables internally.
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*
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* <p> In either case, the quality setting in an <code>ImageWriteParam</code>
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* has the same meaning as for the underlying library: 1.00 means a
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* quantization table of all 1's, 0.75 means the "standard", visually
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* lossless quantization table, and 0.00 means aquantization table of
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* all 255's.
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*
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* <p> While tables for abbreviated streams are often specified by
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* first writing an abbreviated stream containing only the tables, in
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* some applications the tables are fixed ahead of time. This class
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* allows the tables to be specified directly from client code.
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*
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* <p> Normally, the tables are specified in the
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* <code>IIOMetadata</code> objects passed in to the writer, and any
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* tables included in these objects are written to the stream.
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* If no tables are specified in the metadata, then an abbreviated
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* stream is written. If no tables are included in the metadata and
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* no tables are specified in a <code>JPEGImageWriteParam</code>, then
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* an abbreviated stream is encoded using the "standard" visually
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* lossless tables. This class is necessary for specifying tables
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* when an abbreviated stream must be written without writing any tables
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* to a stream first. In order to use this class, the metadata object
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* passed into the writer must contain no tables, and no stream metadata
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* must be provided. See {@link JPEGQTable JPEGQTable} and
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* {@link JPEGHuffmanTable JPEGHuffmanTable} for more
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* information on the default tables.
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*
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* <p> The default <code>JPEGImageWriteParam</code> returned by the
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* <code>getDefaultWriteParam</code> method of the writer contains no
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* tables. Default tables are included in the default
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* <code>IIOMetadata</code> objects returned by the writer.
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*
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* <p> If the metadata does contain tables, the tables given in a
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* <code>JPEGImageWriteParam</code> are ignored. Furthermore, once a
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* set of tables has been written, only tables in the metadata can
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* override them for subsequent writes, whether to the same stream or
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* a different one. In order to specify new tables using this class,
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* the {@link javax.imageio.ImageWriter#reset reset}
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* method of the writer must be called.
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*
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* <p>
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* For more information about the operation of the built-in JPEG plug-ins,
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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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*/
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public class JPEGImageWriteParam extends ImageWriteParam {
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private JPEGQTable[] qTables = null;
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private JPEGHuffmanTable[] DCHuffmanTables = null;
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private JPEGHuffmanTable[] ACHuffmanTables = null;
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private boolean optimizeHuffman = false;
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private String[] compressionNames = {"JPEG"};
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private float[] qualityVals = { 0.00F, 0.30F, 0.75F, 1.00F };
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private String[] qualityDescs = {
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"Low quality", // 0.00 -> 0.30
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"Medium quality", // 0.30 -> 0.75
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"Visually lossless" // 0.75 -> 1.00
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};
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/**
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* Constructs a <code>JPEGImageWriteParam</code>. Tiling is not
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* supported. Progressive encoding is supported. The default
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* progressive mode is MODE_DISABLED. A single form of compression,
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* named "JPEG", is supported. The default compression quality is
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* 0.75.
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*
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* @param locale a <code>Locale</code> to be used by the
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* superclass to localize compression type names and quality
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* descriptions, or <code>null</code>.
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*/
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public JPEGImageWriteParam(Locale locale) {
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super(locale);
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this.canWriteProgressive = true;
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this.progressiveMode = MODE_DISABLED;
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this.canWriteCompressed = true;
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this.compressionTypes = compressionNames;
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this.compressionType = compressionTypes[0];
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this.compressionQuality = JPEG.DEFAULT_QUALITY;
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}
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/**
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* Removes any previous compression quality setting.
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*
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* <p> The default implementation resets the compression quality
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* to <code>0.75F</code>.
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*
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* @exception IllegalStateException if the compression mode is not
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* <code>MODE_EXPLICIT</code>.
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*/
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public void unsetCompression() {
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if (getCompressionMode() != MODE_EXPLICIT) {
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throw new IllegalStateException
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("Compression mode not MODE_EXPLICIT!");
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}
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this.compressionQuality = JPEG.DEFAULT_QUALITY;
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}
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/**
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* Returns <code>false</code> since the JPEG plug-in only supports
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* lossy compression.
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*
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* @return <code>false</code>.
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*
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* @exception IllegalStateException if the compression mode is not
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* <code>MODE_EXPLICIT</code>.
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*/
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public boolean isCompressionLossless() {
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if (getCompressionMode() != MODE_EXPLICIT) {
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throw new IllegalStateException
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("Compression mode not MODE_EXPLICIT!");
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}
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return false;
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}
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public String[] getCompressionQualityDescriptions() {
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if (getCompressionMode() != MODE_EXPLICIT) {
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throw new IllegalStateException
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("Compression mode not MODE_EXPLICIT!");
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}
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if ((getCompressionTypes() != null) &&
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(getCompressionType() == null)) {
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throw new IllegalStateException("No compression type set!");
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}
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return (String[])qualityDescs.clone();
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}
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public float[] getCompressionQualityValues() {
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if (getCompressionMode() != MODE_EXPLICIT) {
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throw new IllegalStateException
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("Compression mode not MODE_EXPLICIT!");
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}
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if ((getCompressionTypes() != null) &&
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(getCompressionType() == null)) {
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throw new IllegalStateException("No compression type set!");
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}
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return (float[])qualityVals.clone();
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}
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/**
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* Returns <code>true</code> if tables are currently set.
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*
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* @return <code>true</code> if tables are present.
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*/
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public boolean areTablesSet() {
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return (qTables != null);
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}
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/**
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* Sets the quantization and Huffman tables to use in encoding
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* abbreviated streams. There may be a maximum of 4 tables of
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* each type. These tables are ignored if tables are specified in
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* the metadata. All arguments must be non-<code>null</code>.
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* The two arrays of Huffman tables must have the same number of
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* elements. The table specifiers in the frame and scan headers
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* in the metadata are assumed to be equivalent to indices into
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* these arrays. The argument arrays are copied by this method.
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*
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* @param qTables An array of quantization table objects.
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* @param DCHuffmanTables An array of Huffman table objects.
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* @param ACHuffmanTables An array of Huffman table objects.
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*
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* @exception IllegalArgumentException if any of the arguments
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* is <code>null</code> or has more than 4 elements, or if the
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* numbers of DC and AC tables differ.
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*
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* @see #unsetEncodeTables
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*/
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public void setEncodeTables(JPEGQTable[] qTables,
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JPEGHuffmanTable[] DCHuffmanTables,
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JPEGHuffmanTable[] ACHuffmanTables) {
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if ((qTables == null) ||
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(DCHuffmanTables == null) ||
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(ACHuffmanTables == null) ||
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(qTables.length > 4) ||
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(DCHuffmanTables.length > 4) ||
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(ACHuffmanTables.length > 4) ||
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(DCHuffmanTables.length != ACHuffmanTables.length)) {
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throw new IllegalArgumentException("Invalid JPEG table arrays");
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}
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this.qTables = (JPEGQTable[])qTables.clone();
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this.DCHuffmanTables = (JPEGHuffmanTable[])DCHuffmanTables.clone();
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this.ACHuffmanTables = (JPEGHuffmanTable[])ACHuffmanTables.clone();
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}
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/**
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* Removes any quantization and Huffman tables that are currently
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* set.
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*
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* @see #setEncodeTables
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*/
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public void unsetEncodeTables() {
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this.qTables = null;
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this.DCHuffmanTables = null;
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this.ACHuffmanTables = null;
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}
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/**
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* Returns a copy of the array of quantization tables set on the
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* most recent call to <code>setEncodeTables</code>, or
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* <code>null</code> if tables are not currently set.
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*
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* @return an array of <code>JPEGQTable</code> objects, or
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* <code>null</code>.
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*
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* @see #setEncodeTables
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*/
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public JPEGQTable[] getQTables() {
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return (qTables != null) ? (JPEGQTable[])qTables.clone() : null;
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}
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/**
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* Returns a copy of the array of DC Huffman tables set on the
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* most recent call to <code>setEncodeTables</code>, or
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* <code>null</code> if tables are not currently set.
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*
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* @return an array of <code>JPEGHuffmanTable</code> objects, or
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* <code>null</code>.
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*
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* @see #setEncodeTables
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*/
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public JPEGHuffmanTable[] getDCHuffmanTables() {
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return (DCHuffmanTables != null)
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? (JPEGHuffmanTable[])DCHuffmanTables.clone()
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: null;
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}
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/**
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* Returns a copy of the array of AC Huffman tables set on the
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* most recent call to <code>setEncodeTables</code>, or
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* <code>null</code> if tables are not currently set.
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*
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* @return an array of <code>JPEGHuffmanTable</code> objects, or
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* <code>null</code>.
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*
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* @see #setEncodeTables
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*/
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public JPEGHuffmanTable[] getACHuffmanTables() {
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return (ACHuffmanTables != null)
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? (JPEGHuffmanTable[])ACHuffmanTables.clone()
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: null;
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}
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/**
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* Tells the writer to generate optimized Huffman tables
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* for the image as part of the writing process. The
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* default is <code>false</code>. If this flag is set
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* to <code>true</code>, it overrides any tables specified
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* in the metadata. Note that this means that any image
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* written with this flag set to <code>true</code> will
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* always contain Huffman tables.
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*
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* @param optimize A boolean indicating whether to generate
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* optimized Huffman tables when writing.
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*
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* @see #getOptimizeHuffmanTables
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*/
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public void setOptimizeHuffmanTables(boolean optimize) {
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optimizeHuffman = optimize;
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}
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/**
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* Returns the value passed into the most recent call
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* to <code>setOptimizeHuffmanTables</code>, or
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* <code>false</code> if <code>setOptimizeHuffmanTables</code>
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* has never been called.
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*
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* @return <code>true</code> if the writer will generate optimized
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* Huffman tables.
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*
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* @see #setOptimizeHuffmanTables
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*/
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public boolean getOptimizeHuffmanTables() {
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return optimizeHuffman;
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}
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}
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