import java.applet.*; 
import java.awt.*; 
import java.awt.image.*; 
import java.awt.event.*; 
import java.net.URL;
import Jama.*;
 
public class SVD extends Applet implements KeyListener {

    private ImageCanvas canvas;
    private Image image;
    private int w, h, r;
    private SingularValueDecomposition svd;

    public void init() { 
	System.err.println("Loading image boat.gif");
	image = getImg("boat.gif");
	w = image.getWidth(this);
	h = image.getHeight(this);
	r = w;
	System.err.println("Computing svd");
	svd = getSVD(image);
	System.err.println("Drawing canvas");
	canvas = new ImageCanvas(image);
	canvas.setRank(r);
	canvas.addKeyListener(this);
	add(canvas);
	System.err.println("Ready: play with the four arrow keys");
    } 

    public SingularValueDecomposition getSVD(Image img) {
	int pixels[] = extractPixelValues(img);
	Matrix m = new Matrix(int2double(pixels), h);
	SingularValueDecomposition svd = m.svd();
	return svd;
    }

    public void updateImage() {
	Matrix U = svd.getU();
	Matrix V = svd.getV();
	Matrix S = svd.getS();
	for (int k = r; k < w; k++) S.set(k, k, 0);
	Matrix A = U.times(S.times(V.transpose()));
	double a[] = A.getColumnPackedCopy();
	image = createImage(double2int(a), w, h);
	canvas.setRank(r);
	canvas.setImage(image);
    }

    public void keyPressed(KeyEvent e) {
	if (e.getKeyCode() == e.VK_UP) {
	    if (r <= w/2) r *= 2;
	} else if (e.getKeyCode() == e.VK_DOWN) {
	    if (r >= 2) r /= 2;
	} else if (e.getKeyCode() == e.VK_LEFT) {
	    if (r >= 2) r--;
	} else if (e.getKeyCode() == e.VK_RIGHT) {
	    if (r < w) r++;
	}
	updateImage();
    }

    public void keyReleased(KeyEvent e) {}
    public void keyTyped(KeyEvent e) {}

    public Image getImg(String fname) {
	Image img = null;
	System.err.println("CodeBase: " + getCodeBase());
	System.err.println("Resource: " + getClass().getResource(fname));
	try {
	  // img = getImage(getCodeBase(), fname);
	  img = getImage(getClass().getResource(fname));
	  waitForImage(img);
	} catch(Exception e) { 
	    System.err.println("Could not get image");
	}
	return img;
    }

    public void waitForImage(Image i)
    {
	MediaTracker tracker = new MediaTracker(this);
	try
	    {
		tracker.addImage(i,0);
		tracker.waitForID(0);
	    }
	catch(InterruptedException e) {System.err.println("Wait interrupted.");}
    }
    
    public int[] extractPixelValues(Image image)
    {
	int width = image.getWidth(this), height = image.getHeight(this);
	int pixels[] = new int[width * height];
	PixelGrabber grabber = new PixelGrabber(image, 0, 0, width, height,
						pixels, 0, width);
	try
	    {
		boolean result = grabber.grabPixels(60000); //bug in PixelGrabber?
		if (!result)
		    {
			System.err.println("Could not grab pixels from image before quantum"+
					   " expired.");
			return pixels;
		    }
	    }
	catch (InterruptedException e) {System.err.println("Grab interrupted.");}

	//each pixel value is of the form alpha, red, green, blue, so we must
	//keep only the last 8 bits to make it fall between 0 and 255.
	for (int k = 0; k < pixels.length; k++) pixels[k] &= 255;

	return pixels;
    }

    public Image createImage(int pixels[], int width, int height)
    {
	int newpixels[] = new int[pixels.length];
	for (int k = 0; k < pixels.length; k++)
	    {
		int a = pixels[k];
		newpixels[k] = (255 << 24) | (a << 16) | (a << 8) | a;
	    }
	Image i = createImage(new MemoryImageSource(width, height, newpixels,
						    0, width));
	return i;
    }

    public double[] int2double(int a[]) {
	double d[] = new double[a.length];
	for (int k = 0; k < a.length; k++)
	    d[k] = (double) a[k];
	return d;
    }

    public int[] double2int(double a[]) {
	int d[] = new int[a.length];
	for (int k = 0; k < a.length; k++) {
	    d[k] = (int) a[k];
	    if (d[k] < 0) d[k] = 0;
	    if (d[k] > 255) d[k] = 255;
	}
	return d;
    }
} 

class ImageCanvas extends Canvas { 
    private Image image = null; 
    private int rank = 0;
    public ImageCanvas(Image i) { 
	setImage(i);
    } 
    public void setImage(Image i) {
	image = i; 
	setSize(i.getWidth(this), i.getHeight(this));
    }
    public void setRank(int i) {
	rank = i;
    }
    public void paint(Graphics g) { 
	if (image == null) return;
	g.drawImage(image, 0, 0, this);
	g.drawString(Integer.toString(rank), 10, 10);
    } 
}