zkoss/zk

/* ImageEncoders.java

    Purpose:
        
    Description:
        
    History:
        Tue Jun 24 16:08:13     2008, Created by tomyeh

Copyright (C) 2008 Potix Corporation. All Rights Reserved.

{{IS_RIGHT
    This program is distributed under LGPL Version 2.1 in the hope that
    it will be useful, but WITHOUT ANY WARRANTY.
}}IS_RIGHT
*/
package org.zkoss.image.encoder;

import java.util.Map;
import java.util.HashMap;
import java.util.Collections;
import org.zkoss.lang.SystemException;

/**
 * The factory of the image encodes.
 *
 * @author tomyeh
 * @since 3.0.7
 */
public class ImageEncoders {
    /** Map(String format, Class encoder). */
    private final static Map<String, Class> _encoders;

    static {
        final Map<String, Class> encoders = new HashMap<String, Class>(4);
        encoders.put("png", PNGEncoder.class);
        encoders.put("jpeg", JPEGEncoder.class);
        _encoders = Collections.synchronizedMap(encoders);
    }

    /** Instantiates and returns the image encoder for the specified format.
     *
     * @param format  The image format of the ZK image being encoded to.
     * It can be "png" or "jpeg".
     * @exception IllegalArgumentException if the encoder of the specified
     * format is not found
     * @exception SystemException if failed to instantiate the encoder
     */
    public static ImageEncoder newInstance(String format) {
        final Class klass = _encoders.get(format.toLowerCase(java.util.Locale.ENGLISH));
        if (klass == null)
            throw new IllegalArgumentException("Unsupported format: "+format);

        try {
            return (ImageEncoder)klass.newInstance();
        } catch (Throwable ex) {
            throw SystemException.Aide.wrap(ex);
        }
    }
    /** Sets the class of the image encoder for the specified format.
     *
     * <p>An instance of the specified class is instantiated each
     * time {@link #newInstance} is called.
     *
     * @param format  The image format of the ZK image being encoded to.
     * It can be "png" or "jpeg".
     * @param klass the class of the image encoder.
     * It must implement {@link ImageEncoder}.
     * @return the previous encoder, or null if not set yet.
     */
    public static Class setEncoderClass(String format, Class klass) {
        if (!ImageEncoder.class.isAssignableFrom(klass))
            throw new IllegalArgumentException(ImageEncoder.class+" must be implemented by "+klass);
        return _encoders.put(format.toLowerCase(java.util.Locale.ENGLISH), klass);
    }
    /** Returns the class of the image encoder for the specified format,
     * or null if not specified yet.
     */
    public static Class getEncoderClass(String format) {
        return _encoders.get(format.toLowerCase(java.util.Locale.ENGLISH));
    }
}