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SWT is an open source widget toolkit for Java designed to provide efficient, portable access to the user-interface facilities of the operating systems on which it is implemented.
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/*******************************************************************************
 * Copyright (c) 2000, 2011 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;
import org.eclipse.swt.internal.image.*;

/**
 * Instances of this class are used to load images from,
 * and save images to, a file or stream.
 * 
 * Currently supported image formats are:
 * 

 * BMP (Windows or OS/2 Bitmap)
 * ICO (Windows Icon)
 * JPEG
 * GIF
 * PNG
 * TIFF
 * 
 * ImageLoaders can be used to:
 * 
 * load/save single images in all formats
 * load/save multiple images (GIF/ICO/TIFF)
 * load/save animated GIF images
 * load interlaced GIF/PNG images
 * load progressive JPEG images
 * 
 *
 * @see SWT Example: ImageAnalyzer
 * @see Sample code and further information
 */
 
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;
	
	/**
	 * This is the compression used when saving jpeg and png files.
	 * 
	 * When saving jpeg files, the value is from 1 to 100, 
	 * where 1 is very high compression but low quality, and 100 is 
	 * no compression and high quality; default is 75.
	 * 

	 * When saving png files, the value is from 0 to 3, but they do not impact the quality 
	 * because PNG is lossless compression. 0 is uncompressed, 1 is low compression and fast,
	 * 2 is default compression, and 3 is high compression but slow.
	 * 
	 * 
	 * @since 3.8
	 */
	public int compression;
		
	/*
	 * 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
 * imageLoaderListeners field.
 */
void reset() {
	data = null;
	logicalScreenWidth = 0;
	logicalScreenHeight = 0;
	backgroundPixel = -1;
	repeatCount = 1;
	compression = -1;
}

/**
 * Loads an array of ImageData 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 ImageData objects loaded from the specified input stream
 *
 * @exception IllegalArgumentException 
 *    ERROR_NULL_ARGUMENT - if the stream is null
 * 
 * @exception SWTException 
 *    ERROR_IO - if an IO error occurs while reading from the stream
 *    ERROR_INVALID_IMAGE - if the image stream contains invalid data
 *    ERROR_UNSUPPORTED_FORMAT - if the image stream contains an unrecognized format
 * 
 */
public ImageData[] load(InputStream stream) {
	if (stream == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	reset();
	data = FileFormat.load(stream, this);
	return data;
}

/**
 * Loads an array of ImageData 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 ImageData objects loaded from the specified file
 *
 * @exception IllegalArgumentException 
 *    ERROR_NULL_ARGUMENT - if the file name is null
 * 
 * @exception SWTException 
 *    ERROR_IO - if an IO error occurs while reading from the file
 *    ERROR_INVALID_IMAGE - if the image file contains invalid data
 *    ERROR_UNSUPPORTED_FORMAT - if the image file contains an unrecognized format
 * 
 */
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:
 * 
 * IMAGE_BMP
 * Windows BMP file format, no compression
 * IMAGE_BMP_RLE
 * Windows BMP file format, RLE compression if appropriate
 * IMAGE_GIF
 * GIF file format
 * IMAGE_ICO
 * Windows ICO file format
 * IMAGE_JPEG
 * JPEG file format
 * IMAGE_PNG
 * PNG file format
 * 
 *
 * @param stream the output stream to write the images to
 * @param format the format to write the images in
 *
 * @exception IllegalArgumentException 
 *    ERROR_NULL_ARGUMENT - if the stream is null
 * 
 * @exception SWTException 
 *    ERROR_IO - if an IO error occurs while writing to the stream
 *    ERROR_INVALID_IMAGE - if the image data contains invalid data
 *    ERROR_UNSUPPORTED_FORMAT - if the image data cannot be saved to the requested format
 * 
 */
public void save(OutputStream stream, int format) {
	if (stream == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	FileFormat.save(stream, format, this);
}

/**
 * Saves the image data in this ImageLoader to a file with the specified name.
 * The format parameter can have one of the following values:
 * 
 * IMAGE_BMP
 * Windows BMP file format, no compression
 * IMAGE_BMP_RLE
 * Windows BMP file format, RLE compression if appropriate
 * IMAGE_GIF
 * GIF file format
 * IMAGE_ICO
 * Windows ICO file format
 * IMAGE_JPEG
 * JPEG file format
 * IMAGE_PNG
 * PNG file format
 * 
 *
 * @param filename the name of the file to write the images to
 * @param format the format to write the images in
 *
 * @exception IllegalArgumentException 
 *    ERROR_NULL_ARGUMENT - if the file name is null
 * 
 * @exception SWTException 
 *    ERROR_IO - if an IO error occurs while writing to the file
 *    ERROR_INVALID_IMAGE - if the image data contains invalid data
 *    ERROR_UNSUPPORTED_FORMAT - if the image data cannot be saved to the requested format
 * 
 */
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.
 * 
 * An ImageLoaderListener should be added before invoking
 * one of the receiver's load methods. The listener's 
 * imageDataLoaded 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 

 *    ERROR_NULL_ARGUMENT - if the listener is null
 * 
 * 
 * @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 
 *    ERROR_NULL_ARGUMENT - if the listener is null
 * 
 * 
 * @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 true if the receiver has image loader
 * listeners, and false otherwise.
 *
 * @return true if there are ImageLoaderListeners, and false 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 ImageLoaderEvent to send to each ImageLoaderListener
 */
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);
	}
}

}