// program to demonstrate animation techniques

import java.awt.*;
import java.applet.*;


public class animate extends Applet implements Runnable 
{
	static final int NUMBER_OF_FRAMES = 36;
	static final int TIME_ASLEEP = 50; // 50 milliseconds sleep time
	
	Image[] gifImages = new Image[NUMBER_OF_FRAMES];
	
	int index = 0;    // index to gifImages array	
	int width = 500;  // width of offscreen graphics area
	int height = 500; // height of offscreen graphics area

	Image        offScreenImage;
	Graphics     offScreenGraphics;
	MediaTracker tracker;
	Thread appletThread;

	public void init()
	{			
		// load images into array
		tracker = new MediaTracker(this);
		for (int index=0; index != gifImages.length; index++)
		{
			gifImages[index] = 
			getImage(getDocumentBase(), "images\\j"+index+".gif");
			tracker.addImage(gifImages[index],index);
		}

		try
		{
			tracker.waitForAll();
		}

		catch (InterruptedException e){}

		offScreenImage = createImage(width,height);
		offScreenGraphics = offScreenImage.getGraphics();
	}
	public void paint(Graphics g)
	{	
		int topLeftX=100;  // abscissa of top left-hand corner of image
		int topLeftY=100;  // ordinate top left-hand corner of image

		// get width and height of image and scale by 50%
		int imageWidth = (gifImages[index].getWidth(this))/2;
		int imageHeight = (gifImages[index].getHeight(this))/2;

		// erase previous image from off screen graphics area
		offScreenGraphics.setColor(Color.white);
		offScreenGraphics.fillRect(0,0,width,height);

		// draw next image in off screen graphics area
		offScreenGraphics.drawImage(gifImages[index],
									    topLeftX, topLeftY,
									    imageWidth, imageHeight,
									    this);		
		
		// draw image on the applet's screen
		g.drawImage(offScreenImage,0,0,width,height,this);		
	}

	// create new thread
	public void start()
	{
		if (appletThread == null)
		{
			appletThread=new Thread(this);
			appletThread.start();
		}
	}
		
	// override run() method to display the images on the screen
	public void run()
	{
		Graphics g = getGraphics();
		while (true)
		{
			paint(g);
			index++;
			index = index % NUMBER_OF_FRAMES;

			try{appletThread.sleep(TIME_ASLEEP);} 
			catch (InterruptedException e){}
		}
	}

	public void destroy()
	{
		if (appletThread != null)
		{
			appletThread.stop();
			appletThread=null;
		}
	}
}