JumbledImageApp.java

import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.imageio.*;
import javax.swing.*;
import java.util.Random;

class JumbledImage extends JComponent {

    private int numlocs = 2;
    private int numcells = numlocs*numlocs;
    private int[] cells;
    private BufferedImage bi;
    int w, h, cw, ch;
    
    public JumbledImage(URL imageSrc) {
        try {
            bi = ImageIO.read(imageSrc);
            w = bi.getWidth(null);
            h = bi.getHeight(null);
        } catch (IOException e) {
            System.out.println("Image could not be read");
//            System.exit(1);
        }
        cw = w/numlocs;
        ch = h/numlocs;
        cells = new int[numcells];
        for (int i=0;i<numcells;i++) {
            cells[i] = i;
        }
    }

    void jumble() {
        Random rand = new Random();
        int ri;
        for (int i=0; i<numcells; i++) {
            while ((ri = rand.nextInt(numlocs)) == i);

            int tmp = cells[i];
            cells[i] = cells[ri];
            cells[ri] = tmp;
        }
    }

    public Dimension getPreferredSize() {
        return new Dimension(w, h);
    }

    public void paintComponent(Graphics g) {
	super.paintComponent(g);

        int dx, dy;
        for (int x=0; x<numlocs; x++) {
            int sx = x*cw;
            for (int y=0; y<numlocs; y++) {
                int sy = y*ch;
                int cell = cells[x*numlocs+y];
                dx = (cell / numlocs) * cw;
                dy = (cell % numlocs) * ch;
                g.drawImage(bi,
                            dx, dy, dx+cw, dy+ch,
                            sx, sy, sx+cw, sy+ch,
                            null);
            }
        }
    }
}

public class JumbledImageApp extends JPanel {

    static String imageFileName = "duke_skateboard.jpg";
    JButton jumbleButton;
    private URL imageSrc;
    private JumbledImage ji;

    public JumbledImageApp() {
             imageSrc = getClass().getResource(imageFileName);
    }
 

    public JumbledImageApp (URL imageSrc) {
        this.imageSrc = imageSrc;
    }

    public void buildUI() {
         ji = new JumbledImage(imageSrc);
        add(ji);
        jumbleButton = new JButton("Jumble");
        jumbleButton.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    JButton b = (JButton)e.getSource();
                    ji.jumble();
                    ji.repaint();
                };
            });
    }

    public static void main(String args[]) {
	String filename = imageFileName;
	if (args.length>0) filename = args[0];
        JFrame f = new JFrame("Jumbled Image");
	f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        URL imageSrc = null;
        try {
             imageSrc = ((new File(filename)).toURI()).toURL();
        } catch (IOException e) {
	    System.out.println(e);
            System.out.println(filename + " not found");
            System.exit(1);
        }
        JumbledImageApp jumbler = new JumbledImageApp();
        jumbler.buildUI();
        f.add(jumbler);
	f.add(jumbler.jumbleButton,BorderLayout.SOUTH);
        f.pack();
        f.setVisible(true);
    }
}