draws a big image scaled to its width-height as specified

/*
 * Copyright (c) 1995-1997 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. Please refer to the file "copyright.html"
 * for further important copyright and licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 */
/*
 * 1.0 code.
 */

import java.applet.*;
import java.awt.*;
import java.awt.image.ImageObserver;

public class ImageUpdater extends Applet {
    /*
     * Written by Jim Graham.
     * This applet draws a big image scaled to its width and height as
     * specified in the <APPLET> tag, and a small image scaled by the
     * same ratio as the big image and positioned in the center of it.
     */
    Image bigimg, smallimg;
    int smallx, smally, smallw, smallh;
    boolean sizeknown = false;
    boolean errored = false;

    public void init() {
        bigimg = getImage(getCodeBase(), "../Big.gif");
        smallimg = getImage(getCodeBase(), "../Small.gif");
        positionImages();
    }

    public boolean imageUpdate(Image theimg, int infoflags,
                               int x, int y, int w, int h) {
        if ((infoflags & (ERROR)) != 0) {
            errored = true;
        }
        if ((infoflags & (WIDTH | HEIGHT)) != 0) {
	    positionImages();
        }
        boolean done = ((infoflags & (ERROR | FRAMEBITS | ALLBITS)) != 0);
        // Repaint immediately if we are done, otherwise batch up
        // repaint requests every 100 milliseconds
        repaint(done ? 0 : 100);
        return !done;
    }

    public synchronized void positionImages() {
	Dimension d = size();
        int bigw = bigimg.getWidth(this);
        int bigh = bigimg.getHeight(this);
        smallw = smallimg.getWidth(this); 
        smallh = smallimg.getHeight(this); 
        if (bigw < 0 || bigh < 0 || smallw < 0 || smallh < 0) {
            return;
        }
        smallw = smallw * d.width / bigw;
        smallh = smallh * d.height / bigh;
        smallx = (d.width - smallw) / 2;
        smally = (d.height - smallh) / 2;
        sizeknown = true;
    }

    public synchronized void paint(Graphics g) {
	Dimension d = size();
        int appw = d.width;
        int apph = d.height;
        if (errored) {
            // The images had a problem - just draw a big red rectangle
            g.setColor(Color.red);
            g.fillRect(0, 0, appw, apph);
            return;
        }
        // Scale the big image to the width and height of the applet
        g.drawImage(bigimg, 0, 0, appw, apph, this);
        if (sizeknown) {
            // Scale the small image to the central region calculated above.
            g.drawImage(smallimg, smallx, smally, smallw, smallh, this);
        }
    }
}