Java tutorial
/* * Copyright (c) 1995, 2017, 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.Image; import java.awt.image.ImageFilter; import java.awt.image.ImageConsumer; import java.awt.image.ImageProducer; import java.util.Hashtable; import java.awt.image.ColorModel; /** * This class is an implementation of the ImageProducer interface which * takes an existing image and a filter object and uses them to produce * image data for a new filtered version of the original image. Furthermore, * {@code FilteredImageSource} is safe for use by multiple threads. * Here is an example which filters an image by swapping the red and * blue components: * <pre> * * Image src = getImage("doc:///demo/images/duke/T1.gif"); * ImageFilter colorfilter = new RedBlueSwapFilter(); * Image img = createImage(new FilteredImageSource(src.getSource(), * colorfilter)); * * </pre> * * @see ImageProducer * * @author Jim Graham */ public class FilteredImageSource implements ImageProducer { ImageProducer src; ImageFilter filter; /** * Constructs an ImageProducer object from an existing ImageProducer * and a filter object. * @param orig the specified {@code ImageProducer} * @param imgf the specified {@code ImageFilter} * @see ImageFilter * @see java.awt.Component#createImage */ public FilteredImageSource(ImageProducer orig, ImageFilter imgf) { src = orig; filter = imgf; } private Hashtable<ImageConsumer, ImageFilter> proxies; /** * Adds the specified {@code ImageConsumer} * to the list of consumers interested in data for the filtered image. * An instance of the original {@code ImageFilter} * is created * (using the filter's {@code getFilterInstance} method) * to manipulate the image data * for the specified {@code ImageConsumer}. * The newly created filter instance * is then passed to the {@code addConsumer} method * of the original {@code ImageProducer}. * * <p> * This method is public as a side effect * of this class implementing * the {@code ImageProducer} interface. * It should not be called from user code, * and its behavior if called from user code is unspecified. * * @param ic the consumer for the filtered image * @see ImageConsumer */ public synchronized void addConsumer(ImageConsumer ic) { if (proxies == null) { proxies = new Hashtable<>(); } if (!proxies.containsKey(ic)) { ImageFilter imgf = filter.getFilterInstance(ic); proxies.put(ic, imgf); src.addConsumer(imgf); } } /** * Determines whether an ImageConsumer is on the list of consumers * currently interested in data for this image. * * <p> * This method is public as a side effect * of this class implementing * the {@code ImageProducer} interface. * It should not be called from user code, * and its behavior if called from user code is unspecified. * * @param ic the specified {@code ImageConsumer} * @return true if the ImageConsumer is on the list; false otherwise * @see ImageConsumer */ public synchronized boolean isConsumer(ImageConsumer ic) { return (proxies != null && proxies.containsKey(ic)); } /** * Removes an ImageConsumer from the list of consumers interested in * data for this image. * * <p> * This method is public as a side effect * of this class implementing * the {@code ImageProducer} interface. * It should not be called from user code, * and its behavior if called from user code is unspecified. * * @see ImageConsumer */ public synchronized void removeConsumer(ImageConsumer ic) { if (proxies != null) { ImageFilter imgf = proxies.get(ic); if (imgf != null) { src.removeConsumer(imgf); proxies.remove(ic); if (proxies.isEmpty()) { proxies = null; } } } } /** * Starts production of the filtered image. * If the specified {@code ImageConsumer} * isn't already a consumer of the filtered image, * an instance of the original {@code ImageFilter} * is created * (using the filter's {@code getFilterInstance} method) * to manipulate the image data * for the {@code ImageConsumer}. * The filter instance for the {@code ImageConsumer} * is then passed to the {@code startProduction} method * of the original {@code ImageProducer}. * * <p> * This method is public as a side effect * of this class implementing * the {@code ImageProducer} interface. * It should not be called from user code, * and its behavior if called from user code is unspecified. * * @param ic the consumer for the filtered image * @see ImageConsumer */ public synchronized void startProduction(ImageConsumer ic) { if (proxies == null) { proxies = new Hashtable<>(); } ImageFilter imgf = proxies.get(ic); if (imgf == null) { imgf = filter.getFilterInstance(ic); proxies.put(ic, imgf); } src.startProduction(imgf); } /** * Requests that a given ImageConsumer have the image data delivered * one more time in top-down, left-right order. The request is * handed to the ImageFilter for further processing, since the * ability to preserve the pixel ordering depends on the filter. * * <p> * This method is public as a side effect * of this class implementing * the {@code ImageProducer} interface. * It should not be called from user code, * and its behavior if called from user code is unspecified. * * @see ImageConsumer */ public synchronized void requestTopDownLeftRightResend(ImageConsumer ic) { if (proxies != null) { ImageFilter imgf = proxies.get(ic); if (imgf != null) { imgf.resendTopDownLeftRight(src); } } } }