Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2006 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.swt.graphics; import java.io.*; import java.util.Vector; import org.eclipse.swt.*; import org.eclipse.swt.internal.Compatibility; /** * Instances of this class are used to load images from, * and save images to, a file or stream. * <p> * Currently supported image formats are: * </p><ul> * <li>BMP (Windows or OS/2 Bitmap)</li> * <li>ICO (Windows Icon)</li> * <li>JPEG</li> * <li>GIF</li> * <li>PNG</li> * <li>TIFF</li> * </ul> * <code>ImageLoaders</code> can be used to: * <ul> * <li>load/save single images in all formats</li> * <li>load/save multiple images (GIF/ICO/TIFF)</li> * <li>load/save animated GIF images</li> * <li>load interlaced GIF/PNG images</li> * <li>load progressive JPEG images</li> * </ul> */ public class ImageLoader { /** * the array of ImageData objects in this ImageLoader. * This array is read in when the load method is called, * and it is written out when the save method is called */ public ImageData[] data; /** * the width of the logical screen on which the images * reside, in pixels (this corresponds to the GIF89a * Logical Screen Width value) */ public int logicalScreenWidth; /** * the height of the logical screen on which the images * reside, in pixels (this corresponds to the GIF89a * Logical Screen Height value) */ public int logicalScreenHeight; /** * the background pixel for the logical screen (this * corresponds to the GIF89a Background Color Index value). * The default is -1 which means 'unspecified background' * */ public int backgroundPixel; /** * the number of times to repeat the display of a sequence * of animated images (this corresponds to the commonly-used * GIF application extension for "NETSCAPE 2.0 01"). * The default is 1. A value of 0 means 'display repeatedly' */ public int repeatCount; /* * the set of ImageLoader event listeners, created on demand */ Vector imageLoaderListeners; /** * Construct a new empty ImageLoader. */ public ImageLoader() { reset(); } /** * Resets the fields of the ImageLoader, except for the * <code>imageLoaderListeners</code> field. */ void reset() { data = null; logicalScreenWidth = 0; logicalScreenHeight = 0; backgroundPixel = -1; repeatCount = 1; } /** * Loads an array of <code>ImageData</code> objects from the * specified input stream. Throws an error if either an error * occurs while loading the images, or if the images are not * of a supported type. Returns the loaded image data array. * * @param stream the input stream to load the images from * @return an array of <code>ImageData</code> objects loaded from the specified input stream * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the stream is null</li> * </ul> * @exception SWTException <ul> * <li>ERROR_IO - if an IO error occurs while reading from the stream</li> * <li>ERROR_INVALID_IMAGE - if the image stream contains invalid data</li> * <li>ERROR_UNSUPPORTED_FORMAT - if the image stream contains an unrecognized format</li> * </ul> */ public ImageData[] load(InputStream stream) { SWT.error(SWT.ERROR_NULL_ARGUMENT); return null; } /** * Loads an array of <code>ImageData</code> objects from the * file with the specified name. Throws an error if either * an error occurs while loading the images, or if the images are * not of a supported type. Returns the loaded image data array. * * @param filename the name of the file to load the images from * @return an array of <code>ImageData</code> objects loaded from the specified file * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the file name is null</li> * </ul> * @exception SWTException <ul> * <li>ERROR_IO - if an IO error occurs while reading from the file</li> * <li>ERROR_INVALID_IMAGE - if the image file contains invalid data</li> * <li>ERROR_UNSUPPORTED_FORMAT - if the image file contains an unrecognized format</li> * </ul> */ public ImageData[] load(String filename) { if (filename == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); InputStream stream = null; try { stream = Compatibility.newFileInputStream(filename); return load(stream); } catch (IOException e) { SWT.error(SWT.ERROR_IO, e); } finally { try { if (stream != null) stream.close(); } catch (IOException e) { // Ignore error } } return null; } /** * Saves the image data in this ImageLoader to the specified stream. * The format parameter can have one of the following values: * <dl> * <dt><code>IMAGE_BMP</code></dt> * <dd>Windows BMP file format, no compression</dd> * <dt><code>IMAGE_BMP_RLE</code></dt> * <dd>Windows BMP file format, RLE compression if appropriate</dd> * <dt><code>IMAGE_GIF</code></dt> * <dd>GIF file format</dd> * <dt><code>IMAGE_ICO</code></dt> * <dd>Windows ICO file format</dd> * <dt><code>IMAGE_JPEG</code></dt> * <dd>JPEG file format</dd> * <dt><code>IMAGE_PNG</code></dt> * <dd>PNG file format</dd> * </dl> * * @param stream the output stream to write the images to * @param format the format to write the images in * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the stream is null</li> * </ul> * @exception SWTException <ul> * <li>ERROR_IO - if an IO error occurs while writing to the stream</li> * <li>ERROR_INVALID_IMAGE - if the image data contains invalid data</li> * <li>ERROR_UNSUPPORTED_FORMAT - if the image data cannot be saved to the requested format</li> * </ul> */ public void save(OutputStream stream, int format) { SWT.error(SWT.ERROR_NULL_ARGUMENT); } /** * Saves the image data in this ImageLoader to a file with the specified name. * The format parameter can have one of the following values: * <dl> * <dt><code>IMAGE_BMP</code></dt> * <dd>Windows BMP file format, no compression</dd> * <dt><code>IMAGE_BMP_RLE</code></dt> * <dd>Windows BMP file format, RLE compression if appropriate</dd> * <dt><code>IMAGE_GIF</code></dt> * <dd>GIF file format</dd> * <dt><code>IMAGE_ICO</code></dt> * <dd>Windows ICO file format</dd> * <dt><code>IMAGE_JPEG</code></dt> * <dd>JPEG file format</dd> * <dt><code>IMAGE_PNG</code></dt> * <dd>PNG file format</dd> * </dl> * * @param filename the name of the file to write the images to * @param format the format to write the images in * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the file name is null</li> * </ul> * @exception SWTException <ul> * <li>ERROR_IO - if an IO error occurs while writing to the file</li> * <li>ERROR_INVALID_IMAGE - if the image data contains invalid data</li> * <li>ERROR_UNSUPPORTED_FORMAT - if the image data cannot be saved to the requested format</li> * </ul> */ public void save(String filename, int format) { if (filename == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); OutputStream stream = null; try { stream = Compatibility.newFileOutputStream(filename); } catch (IOException e) { SWT.error(SWT.ERROR_IO, e); } save(stream, format); try { stream.close(); } catch (IOException e) { } } /** * Adds the listener to the collection of listeners who will be * notified when image data is either partially or completely loaded. * <p> * An ImageLoaderListener should be added before invoking * one of the receiver's load methods. The listener's * <code>imageDataLoaded</code> method is called when image * data has been partially loaded, as is supported by interlaced * GIF/PNG or progressive JPEG images. * * @param listener the listener which should be notified * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the listener is null</li> * </ul> * * @see ImageLoaderListener * @see ImageLoaderEvent */ public void addImageLoaderListener(ImageLoaderListener listener) { if (listener == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); if (imageLoaderListeners == null) { imageLoaderListeners = new Vector(); } imageLoaderListeners.addElement(listener); } /** * Removes the listener from the collection of listeners who will be * notified when image data is either partially or completely loaded. * * @param listener the listener which should no longer be notified * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the listener is null</li> * </ul> * * @see #addImageLoaderListener(ImageLoaderListener) */ public void removeImageLoaderListener(ImageLoaderListener listener) { if (listener == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); if (imageLoaderListeners == null) return; imageLoaderListeners.removeElement(listener); } /** * Returns <code>true</code> if the receiver has image loader * listeners, and <code>false</code> otherwise. * * @return <code>true</code> if there are <code>ImageLoaderListener</code>s, and <code>false</code> otherwise * * @see #addImageLoaderListener(ImageLoaderListener) * @see #removeImageLoaderListener(ImageLoaderListener) */ public boolean hasListeners() { return imageLoaderListeners != null && imageLoaderListeners.size() > 0; } /** * Notifies all image loader listeners that an image loader event * has occurred. Pass the specified event object to each listener. * * @param event the <code>ImageLoaderEvent</code> to send to each <code>ImageLoaderListener</code> */ public void notifyListeners(ImageLoaderEvent event) { if (!hasListeners()) return; int size = imageLoaderListeners.size(); for (int i = 0; i < size; i++) { ImageLoaderListener listener = (ImageLoaderListener) imageLoaderListeners.elementAt(i); listener.imageDataLoaded(event); } } }