imageencoderfactory.java

来自「JfreeChart 常用图表例子」· Java 代码 · 共 165 行

/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
 *
 * Project Info:  http://www.jfree.org/jfreechart/index.html
 *
 * This library is free software; you can redistribute it and/or modify it 
 * under the terms of the GNU Lesser General Public License as published by 
 * the Free Software Foundation; either version 2.1 of the License, or 
 * (at your option) any later version.
 *
 * This library 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 Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License 
 * along with this library; if not, write to the Free Software Foundation, 
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * ------------------------
 * ImageEncoderFactory.java
 * ------------------------
 * (C) Copyright 2004, by Richard Atkinson and Contributors.
 *
 * Original Author:  Richard Atkinson;
 * Contributor(s):   -;
 *
 * $Id: ImageEncoderFactory.java,v 1.3 2005/03/28 19:38:57 mungady Exp $
 *
 * Changes
 * -------
 * 01-Aug-2004 : Initial version (RA);
 *
 */

package org.jfree.chart.encoders;

import java.util.Hashtable;

/**
 * Factory class for returning {@link ImageEncoder}s for different 
 * {@link ImageFormat}s.
 *
 * @author Richard Atkinson
 */
public class ImageEncoderFactory {
    private static Hashtable encoders = null;

    static {
        init();
    }

    /**
     * Sets up default encoders (uses Sun PNG Encoder if JDK 1.4+ and the
     * SunPNGEncoderAdapter class is available).
     */
    private static void init() {
        encoders = new Hashtable();
        encoders.put("jpeg", "org.jfree.chart.encoders.SunJPEGEncoderAdapter");
        try {
            //  Test for being run under JDK 1.4+
            Class.forName("javax.imageio.ImageIO");
            //  Test for JFreeChart being compiled under JDK 1.4+
            Class.forName("org.jfree.chart.encoders.SunPNGEncoderAdapter");
            encoders.put(
                "png", "org.jfree.chart.encoders.SunPNGEncoderAdapter"
            );
        } 
        catch (ClassNotFoundException e) {
            encoders.put(
                "png", "org.jfree.chart.encoders.KeypointPNGEncoderAdapter"
            );
        }
    }

    /**
     * Used to set additional encoders or replace default ones.
     *
     * @param format  The image format name.
     * @param imageEncoderClassName  The name of the ImageEncoder class.
     */
    public static void setImageEncoder(String format, 
                                       String imageEncoderClassName) {
        encoders.put(format, imageEncoderClassName);
    }

    /**
     * Used to retrieve an ImageEncoder for a specific image format.
     *
     * @param format  The image format required.
     * 
     * @return The ImageEncoder or <code>null</code> if none available.
     */
    public static ImageEncoder newInstance(String format) {
        ImageEncoder imageEncoder = null;
        String className = (String) encoders.get(format);
        if (className == null) {
            throw new IllegalArgumentException(
                "Unsupported image format - " + format
            );
        }
        try {
            Class imageEncoderClass = Class.forName(className);
            imageEncoder = (ImageEncoder) imageEncoderClass.newInstance();
        } 
        catch (Exception e) {
            throw new IllegalArgumentException(e.toString());
        }
        return imageEncoder;
    }

    /**
     * Used to retrieve an ImageEncoder for a specific image format.
     *
     * @param format  The image format required.
     * @param quality  The quality to be set before returning.
     * 
     * @return The ImageEncoder or <code>null</code> if none available.
     */
    public static ImageEncoder newInstance(String format, float quality) {
        ImageEncoder imageEncoder = newInstance(format);
        imageEncoder.setQuality(quality);
        return imageEncoder;
    }

    /**
     * Used to retrieve an ImageEncoder for a specific image format.
     *
     * @param format  The image format required.
     * @param encodingAlpha  Sets whether alpha transparency should be encoded.
     * 
     * @return The ImageEncoder or <code>null</code> if none available.
     */
    public static ImageEncoder newInstance(String format, 
                                           boolean encodingAlpha) {
        ImageEncoder imageEncoder = newInstance(format);
        imageEncoder.setEncodingAlpha(encodingAlpha);
        return imageEncoder;
    }

    /**
     * Used to retrieve an ImageEncoder for a specific image format.
     *
     * @param format  The image format required.
     * @param quality  The quality to be set before returning.
     * @param encodingAlpha  Sets whether alpha transparency should be encoded.
     * 
     * @return The ImageEncoder or <code>null</code> if none available.
     */
    public static ImageEncoder newInstance(String format, float quality, 
                                           boolean encodingAlpha) {
        ImageEncoder imageEncoder = newInstance(format);
        imageEncoder.setQuality(quality);
        imageEncoder.setEncodingAlpha(encodingAlpha);
        return imageEncoder;
    }

}