https://openjdk.java.net/ 
/*
 * Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package javax.imageio.plugins.jpeg;

import java.util.Locale;
import javax.imageio.ImageWriteParam;

import com.sun.imageio.plugins.jpeg.JPEG;


This class adds the ability to set JPEG quantization and Huffman tables when using the built-in JPEG writer plug-in, and to request that optimized Huffman tables be computed for an image. An instance of this class will be returned from the getDefaultImageWriteParam methods of the built-in JPEG ImageWriter. 
 The principal purpose of these additions is to allow the specification of tables to use in encoding abbreviated streams. The built-in JPEG writer will also accept an ordinary ImageWriteParam, in which case the writer will construct the necessary tables internally. 
 In either case, the quality setting in an ImageWriteParam has the same meaning as for the underlying library: 1.00 means a quantization table of all 1's, 0.75 means the "standard", visually lossless quantization table, and 0.00 means aquantization table of all 255's. 
 While tables for abbreviated streams are often specified by
first writing an abbreviated stream containing only the tables, in
some applications the tables are fixed ahead of time.  This class
allows the tables to be specified directly from client code.

 Normally, the tables are specified in the IIOMetadata objects passed in to the writer, and any tables included in these objects are written to the stream. If no tables are specified in the metadata, then an abbreviated stream is written. If no tables are included in the metadata and no tables are specified in a JPEGImageWriteParam, then an abbreviated stream is encoded using the "standard" visually lossless tables. This class is necessary for specifying tables when an abbreviated stream must be written without writing any tables to a stream first. In order to use this class, the metadata object passed into the writer must contain no tables, and no stream metadata must be provided. See JPEGQTable and JPEGHuffmanTable for more information on the default tables. 
 The default JPEGImageWriteParam returned by the getDefaultWriteParam method of the writer contains no tables. Default tables are included in the default IIOMetadata objects returned by the writer. 
 If the metadata does contain tables, the tables given in a JPEGImageWriteParam are ignored. Furthermore, once a set of tables has been written, only tables in the metadata can override them for subsequent writes, whether to the same stream or a different one. In order to specify new tables using this class, the reset method of the writer must be called. 

For more information about the operation of the built-in JPEG plug-ins,
see the JPEG
metadata format specification and usage notes.

/**
 * This class adds the ability to set JPEG quantization and Huffman
 * tables when using the built-in JPEG writer plug-in, and to request that
 * optimized Huffman tables be computed for an image.  An instance of
 * this class will be returned from the
 * {@code getDefaultImageWriteParam} methods of the built-in JPEG
 * {@code ImageWriter}.

 * <p> The principal purpose of these additions is to allow the
 * specification of tables to use in encoding abbreviated streams.
 * The built-in JPEG writer will also accept an ordinary
 * {@code ImageWriteParam}, in which case the writer will
 * construct the necessary tables internally.
 *
 * <p> In either case, the quality setting in an {@code ImageWriteParam}
 * has the same meaning as for the underlying library: 1.00 means a
 * quantization table of all 1's, 0.75 means the "standard", visually
 * lossless quantization table, and 0.00 means aquantization table of
 * all 255's.
 *
 * <p> While tables for abbreviated streams are often specified by
 * first writing an abbreviated stream containing only the tables, in
 * some applications the tables are fixed ahead of time.  This class
 * allows the tables to be specified directly from client code.
 *
 * <p> Normally, the tables are specified in the
 * {@code IIOMetadata} objects passed in to the writer, and any
 * tables included in these objects are written to the stream.
 * If no tables are specified in the metadata, then an abbreviated
 * stream is written.  If no tables are included in the metadata and
 * no tables are specified in a {@code JPEGImageWriteParam}, then
 * an abbreviated stream is encoded using the "standard" visually
 * lossless tables.  This class is necessary for specifying tables
 * when an abbreviated stream must be written without writing any tables
 * to a stream first.  In order to use this class, the metadata object
 * passed into the writer must contain no tables, and no stream metadata
 * must be provided.  See {@link JPEGQTable JPEGQTable} and
 * {@link JPEGHuffmanTable JPEGHuffmanTable} for more
 * information on the default tables.
 *
 * <p> The default {@code JPEGImageWriteParam} returned by the
 * {@code getDefaultWriteParam} method of the writer contains no
 * tables.  Default tables are included in the default
 * {@code IIOMetadata} objects returned by the writer.
 *
 * <p> If the metadata does contain tables, the tables given in a
 * {@code JPEGImageWriteParam} are ignored.  Furthermore, once a
 * set of tables has been written, only tables in the metadata can
 * override them for subsequent writes, whether to the same stream or
 * a different one.  In order to specify new tables using this class,
 * the {@link javax.imageio.ImageWriter#reset reset}
 * method of the writer must be called.
 *
 * <p>
 * For more information about the operation of the built-in JPEG plug-ins,
 * see the <A HREF="../../metadata/doc-files/jpeg_metadata.html">JPEG
 * metadata format specification and usage notes</A>.
 *
 */
public class JPEGImageWriteParam extends ImageWriteParam {

    private JPEGQTable[] qTables = null;
    private JPEGHuffmanTable[] DCHuffmanTables = null;
    private JPEGHuffmanTable[] ACHuffmanTables = null;
    private boolean optimizeHuffman = false;
    private String[] compressionNames = {"JPEG"};
    private float[] qualityVals = { 0.00F, 0.30F, 0.75F, 1.00F };
    private String[] qualityDescs = {
        "Low quality",       // 0.00 -> 0.30
        "Medium quality",    // 0.30 -> 0.75
        "Visually lossless"  // 0.75 -> 1.00
    };

    
Constructs a JPEGImageWriteParam. Tiling is not supported. Progressive encoding is supported. The default progressive mode is MODE_DISABLED. A single form of compression, named "JPEG", is supported. The default compression quality is 0.75. 
Params:
  • locale – a Locale to be used by the superclass to localize compression type names and quality descriptions, or null.
/**
     * Constructs a {@code JPEGImageWriteParam}.  Tiling is not
     * supported.  Progressive encoding is supported. The default
     * progressive mode is MODE_DISABLED.  A single form of compression,
     * named "JPEG", is supported.  The default compression quality is
     * 0.75.
     *
     * @param locale a {@code Locale} to be used by the
     * superclass to localize compression type names and quality
     * descriptions, or {@code null}.
     */
    public JPEGImageWriteParam(Locale locale) {
        super(locale);
        this.canWriteProgressive = true;
        this.progressiveMode = MODE_DISABLED;
        this.canWriteCompressed = true;
        this.compressionTypes = compressionNames;
        this.compressionType = compressionTypes[0];
        this.compressionQuality = JPEG.DEFAULT_QUALITY;
    }

    
Removes any previous compression quality setting.

 The default implementation resets the compression quality to 0.75F. 
Throws:
/**
     * Removes any previous compression quality setting.
     *
     * <p> The default implementation resets the compression quality
     * to {@code 0.75F}.
     *
     * @exception IllegalStateException if the compression mode is not
     * {@code MODE_EXPLICIT}.
     */
    public void unsetCompression() {
        if (getCompressionMode() != MODE_EXPLICIT) {
            throw new IllegalStateException
                ("Compression mode not MODE_EXPLICIT!");
        }
        this.compressionQuality = JPEG.DEFAULT_QUALITY;
    }

    
Returns false since the JPEG plug-in only supports lossy compression. 
Throws:
Returns:false.
/**
     * Returns {@code false} since the JPEG plug-in only supports
     * lossy compression.
     *
     * @return {@code false}.
     *
     * @exception IllegalStateException if the compression mode is not
     * {@code MODE_EXPLICIT}.
     */
    public boolean isCompressionLossless() {
        if (getCompressionMode() != MODE_EXPLICIT) {
            throw new IllegalStateException
                ("Compression mode not MODE_EXPLICIT!");
        }
        return false;
    }

    public String[] getCompressionQualityDescriptions() {
        if (getCompressionMode() != MODE_EXPLICIT) {
            throw new IllegalStateException
                ("Compression mode not MODE_EXPLICIT!");
        }
        if ((getCompressionTypes() != null) &&
            (getCompressionType() == null)) {
            throw new IllegalStateException("No compression type set!");
        }
        return qualityDescs.clone();
    }

    public float[] getCompressionQualityValues() {
        if (getCompressionMode() != MODE_EXPLICIT) {
            throw new IllegalStateException
                ("Compression mode not MODE_EXPLICIT!");
        }
        if ((getCompressionTypes() != null) &&
            (getCompressionType() == null)) {
            throw new IllegalStateException("No compression type set!");
        }
        return qualityVals.clone();
    }
    
Returns true if tables are currently set. 
Returns:true if tables are present.
/**
     * Returns {@code true} if tables are currently set.
     *
     * @return {@code true} if tables are present.
     */
    public boolean areTablesSet() {
        return (qTables != null);
    }

    
Sets the quantization and Huffman tables to use in encoding abbreviated streams. There may be a maximum of 4 tables of each type. These tables are ignored if tables are specified in the metadata. All arguments must be non-null. The two arrays of Huffman tables must have the same number of elements. The table specifiers in the frame and scan headers in the metadata are assumed to be equivalent to indices into these arrays. The argument arrays are copied by this method. 
Params:
  • qTables – An array of quantization table objects.
  • DCHuffmanTables – An array of Huffman table objects.
  • ACHuffmanTables – An array of Huffman table objects.
Throws:
  • IllegalArgumentException – if any of the arguments is null or has more than 4 elements, or if the numbers of DC and AC tables differ.
See Also:
/**
     * Sets the quantization and Huffman tables to use in encoding
     * abbreviated streams.  There may be a maximum of 4 tables of
     * each type.  These tables are ignored if tables are specified in
     * the metadata.  All arguments must be non-{@code null}.
     * The two arrays of Huffman tables must have the same number of
     * elements.  The table specifiers in the frame and scan headers
     * in the metadata are assumed to be equivalent to indices into
     * these arrays.  The argument arrays are copied by this method.
     *
     * @param qTables An array of quantization table objects.
     * @param DCHuffmanTables An array of Huffman table objects.
     * @param ACHuffmanTables An array of Huffman table objects.
     *
     * @exception IllegalArgumentException if any of the arguments
     * is {@code null} or has more than 4 elements, or if the
     * numbers of DC and AC tables differ.
     *
     * @see #unsetEncodeTables
     */
    public void setEncodeTables(JPEGQTable[] qTables,
                                JPEGHuffmanTable[] DCHuffmanTables,
                                JPEGHuffmanTable[] ACHuffmanTables) {
        if ((qTables == null) ||
            (DCHuffmanTables == null) ||
            (ACHuffmanTables == null) ||
            (qTables.length > 4) ||
            (DCHuffmanTables.length > 4) ||
            (ACHuffmanTables.length > 4) ||
            (DCHuffmanTables.length != ACHuffmanTables.length)) {
                throw new IllegalArgumentException("Invalid JPEG table arrays");
        }
        this.qTables = qTables.clone();
        this.DCHuffmanTables = DCHuffmanTables.clone();
        this.ACHuffmanTables = ACHuffmanTables.clone();
    }

    
Removes any quantization and Huffman tables that are currently
set.

See Also:
  • setEncodeTables
/**
     * Removes any quantization and Huffman tables that are currently
     * set.
     *
     * @see #setEncodeTables
     */
    public void unsetEncodeTables() {
        this.qTables = null;
        this.DCHuffmanTables = null;
        this.ACHuffmanTables = null;
    }

    
Returns a copy of the array of quantization tables set on the most recent call to setEncodeTables, or null if tables are not currently set. 
See Also:
Returns:an array of JPEGQTable objects, or null.
/**
     * Returns a copy of the array of quantization tables set on the
     * most recent call to {@code setEncodeTables}, or
     * {@code null} if tables are not currently set.
     *
     * @return an array of {@code JPEGQTable} objects, or
     * {@code null}.
     *
     * @see #setEncodeTables
     */
    public JPEGQTable[] getQTables() {
        return (qTables != null) ? qTables.clone() : null;
    }

    
Returns a copy of the array of DC Huffman tables set on the most recent call to setEncodeTables, or null if tables are not currently set. 
See Also:
Returns:an array of JPEGHuffmanTable objects, or null.
/**
     * Returns a copy of the array of DC Huffman tables set on the
     * most recent call to {@code setEncodeTables}, or
     * {@code null} if tables are not currently set.
     *
     * @return an array of {@code JPEGHuffmanTable} objects, or
     * {@code null}.
     *
     * @see #setEncodeTables
     */
    public JPEGHuffmanTable[] getDCHuffmanTables() {
        return (DCHuffmanTables != null)
            ? DCHuffmanTables.clone()
            : null;
    }

    
Returns a copy of the array of AC Huffman tables set on the most recent call to setEncodeTables, or null if tables are not currently set. 
See Also:
Returns:an array of JPEGHuffmanTable objects, or null.
/**
     * Returns a copy of the array of AC Huffman tables set on the
     * most recent call to {@code setEncodeTables}, or
     * {@code null} if tables are not currently set.
     *
     * @return an array of {@code JPEGHuffmanTable} objects, or
     * {@code null}.
     *
     * @see #setEncodeTables
     */
    public JPEGHuffmanTable[] getACHuffmanTables() {
        return (ACHuffmanTables != null)
            ? ACHuffmanTables.clone()
            : null;
    }

    
Tells the writer to generate optimized Huffman tables for the image as part of the writing process. The default is false. If this flag is set to true, it overrides any tables specified in the metadata. Note that this means that any image written with this flag set to true will always contain Huffman tables. 
Params:
  • optimize – A boolean indicating whether to generate
optimized Huffman tables when writing.
See Also:
/**
     * Tells the writer to generate optimized Huffman tables
     * for the image as part of the writing process.  The
     * default is {@code false}.  If this flag is set
     * to {@code true}, it overrides any tables specified
     * in the metadata.  Note that this means that any image
     * written with this flag set to {@code true} will
     * always contain Huffman tables.
     *
     * @param optimize A boolean indicating whether to generate
     * optimized Huffman tables when writing.
     *
     * @see #getOptimizeHuffmanTables
     */
    public void setOptimizeHuffmanTables(boolean optimize) {
        optimizeHuffman = optimize;
    }

    
Returns the value passed into the most recent call to setOptimizeHuffmanTables, or false if setOptimizeHuffmanTables has never been called. 
See Also:
Returns:true if the writer will generate optimized Huffman tables.
/**
     * Returns the value passed into the most recent call
     * to {@code setOptimizeHuffmanTables}, or
     * {@code false} if {@code setOptimizeHuffmanTables}
     * has never been called.
     *
     * @return {@code true} if the writer will generate optimized
     * Huffman tables.
     *
     * @see #setOptimizeHuffmanTables
     */
    public boolean getOptimizeHuffmanTables() {
        return optimizeHuffman;
    }
}