/*
 * Copyright (c) 2015, 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 java.awt.image;

import java.awt.Graphics;
import java.awt.Image;

/**
 * This class provides default implementations of several {@code Image} methods
 * for classes that want to implement the {@MultiResolutionImage} interface.
 *
 * For example,
 * <pre> {@code
 * public class CustomMultiResolutionImage extends AbstractMultiResolutionImage {
 *
 *     final Image[] resolutionVariants;
 *
 *     public CustomMultiResolutionImage(Image... resolutionVariants) {
 *          this.resolutionVariants = resolutionVariants;
 *     }
 *
 *     public Image getResolutionVariant(
 *             double destImageWidth, double destImageHeight) {
 *         // return a resolution variant based on the given destination image size
 *     }
 *
 *     public List<Image> getResolutionVariants() {
 *         return Collections.unmodifiableList(Arrays.asList(resolutionVariants));
 *     }
 *
 *     protected Image getBaseImage() {
 *         return resolutionVariants[0];
 *     }
 * }
 * } </pre>
 *
 * @see java.awt.Image
 * @see java.awt.image.MultiResolutionImage
 *
 * @since 9
 */
public abstract class AbstractMultiResolutionImage extends java.awt.Image
        implements MultiResolutionImage {

    /**
     * Returns the width of the base image. If the width is not yet known,
     * this method returns <code>-1</code> and the specified
     * <code>ImageObserver</code> object is notified later.
     * @param observer an object waiting for the image to be loaded.
     * @return the width of this image, or <code>-1</code>
     * if the width is not yet known.
     */
    
    @Override
    public int getWidth(ImageObserver observer) {
        return getBaseImage().getWidth(observer);
    }
    
    /**
     * Returns the height of the base image. If the height is not yet known,
     * this method returns <code>-1</code> and the specified
     * <code>ImageObserver</code> object is notified later.
     * @param observer an object waiting for the image to be loaded.
     * @return the height of this image, or <code>-1</code>
     * if the height is not yet known.
     */
    
    @Override
    public int getHeight(ImageObserver observer) {
        return getBaseImage().getHeight(observer);
    }

    /**
     * Gets the object that produces the pixels for the base image.
     * This method is called by the image filtering classes and by
     * methods that perform image conversion and scaling.
     * @return the {@code ImageProducer} that produces the pixels
     * for this image.
     */
    
    @Override
    public ImageProducer getSource() {
        return getBaseImage().getSource();
    }
    
     /**
     * This method is not supported by {@code AbstractMultiResolutionImage}
     * and always throws {@code UnsupportedOperationException}
     *
     * @return {@code UnsupportedOperationException} is thrown
     * @throws UnsupportedOperationException this method is not supported
     */
    
    @Override
    public Graphics getGraphics() {
        throw new UnsupportedOperationException("getGraphics() not supported"
                + " on Multi-Resolution Images");
    }

    /**
     * Gets a property of this image by name.
     * 
     * Individual property names are defined by the various image
     * formats. If a property is not defined for a particular image, this
     * method returns the {@code UndefinedProperty} object.
     * 
     * If the properties for this image are not yet known, this method
     * returns {@code null}, and the {@code ImageObserver}
     * object is notified later.
     * 
     * The property name {@code "comment"} should be used to store
     * an optional comment which can be presented to the application as a
     * description of the image, its source, or its author.
     * @param name a property name.
     * @param observer an object waiting for this image to be loaded.
     * @return the value of the named property if the property name is not null.
     * @throws      NullPointerException if the property name is null.
     */
    
    @Override
    public Object getProperty(String name, ImageObserver observer) {
        return getBaseImage().getProperty(name, observer);
    }

    /**
     * Return the base image representing the best version of the image for
     * rendering at the default width and height.
     *
     * @return the base image of the set of multi-resolution images
     *
     * @since 9
     */
    protected abstract Image getBaseImage();
}