Java 1.2 How-To/JavaHowTo.iso/javafile/ch07/Mandelbrot.java

Java Source | 1998-12-14 | 5.6 KB | 272 lines

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;

/*
 * a class for generating and displaying the
 * Mandelbrot set
 */
public class Mandelbrot extends Applet implements MouseListener,
                        MouseMotionListener, ActionListener
{

/*
 * the maximum number of colors for
 * each pixel
 */
final int MaxColors = 256;

/*
 * the width and height of the image
 */
int mWidth, mHeight;

/*
 * the array of pixel values
 */
int pixels[];

/*
 * the set values
 */
int mandelSet[];

/*
 * the image produce by the set
 */
Image theImage = null;

/*
 * the mapping function from set values to pixel values
 */
int pixMap[] = new int[MaxColors];

/*
 * a flag used for recalculating
 */
boolean startCalculate = false;

/*
 * instance of MandelRect class
 */
MandelRect mandelRect;

/*
 * the control buttons
 */
Button startButton;
Button zoomButton;

/*
 * called when the applet is loaded
 * initialize the pixmap array and add user interface
 */
public void init () {

    mWidth = 100;
    mHeight = 100;
    pixels = new int [mWidth * mHeight];
    mandelSet = new int [mWidth * mHeight];

    mandelRect = new MandelRect (mWidth, mHeight);

    int red, green, blue;
    int i;

    pixMap[0] = 0xffffffff;
    for (i=1; i<MaxColors-1; i+=1) {
        red = i;
        green = (i<128) ? i << 1 : 255-(i<<1);
        blue = MaxColors-i;
        pixMap[i] = (255 << 24) | (red << 16) | (green << 8) | blue;
    }
    pixMap[MaxColors-1] = 0xff000000;

    setLayout(new BorderLayout());

    startButton = new Button ("Start over");
    zoomButton = new Button ("Zoom in");
    startButton.addActionListener(this);
    zoomButton.addActionListener(this);
    addMouseListener(this);
    addMouseMotionListener(this);

    Panel p = new Panel ();
    p.setLayout (new FlowLayout ());
    p.add (startButton);
    p.add (zoomButton);
    add ("South", p);
}

/*
 * called when the applet is started
 * forces a recalculation of the set
 */
public void start () {

    startCalculate = true;
    repaint ();
}

/*
 * call update for efficiency
 * @param g - destination graphics object
 */
public void paint (Graphics g) {

    update (g);
}

/**
 * override default update() method to avoid erase flicker
 * @param g - destination graphics object
 */
public void update (Graphics g) {

    if (startCalculate) {
        calculate ();
        startCalculate = false;
    }
    if (theImage != null) g.drawImage (theImage, 0, 0, this);
    else repaint (1000);
    mandelRect.paint (g);
}

/*
 * perform the actual set calculation
 */
void calculate () {

    int i, index;
    double width, height;
    double row, col;
    double zr, zi, cr, ci, tzr, tzi;
    double hFactor, vFactor;
    double x, y;

    theImage = null;

    x = mandelRect.mandelX;
    y = mandelRect.mandelY;
    width = (double) mandelRect.imgWidth;
    height = (double) mandelRect.imgHeight;
    hFactor = mandelRect.mandelWidth/width;
    vFactor = mandelRect.mandelHeight/height;

    index = 0;
    for (row=0; row<height; row+=1) {
        for (col=0; col<width; col+=1) {
            zr = 0;
            zi = 0;
            cr = x + col * hFactor;
            ci = y + row * vFactor;
            for (i=1; i<64; i+=1) {
                tzr = zr*zr - zi*zi + cr;
                tzi = 2*zr*zi + ci;
                zr = tzr;
                zi = tzi;
                if (zr*zr + zi*zi > 4.0) break;
            }
            mandelSet[index++] = (i << 2)-1;
        }
    }

    for (i=0; i<mWidth*mHeight; i+=1) {
        pixels[i] = pixMap[mandelSet[i]];
    }

    theImage = createImage (
        new MemoryImageSource(mWidth, mHeight, pixels, 0, mWidth));
}

public void mouseClicked(MouseEvent e){}
public void mouseEntered(MouseEvent e){}
public void mouseExited(MouseEvent e){}

public void mouseReleased(MouseEvent e)
{
    int x =e.getX();
    int y =e.getY();

    mandelRect.setWidthHeight (x, y);
    mandelRect.setPaintRect (true);
    repaint ();
}

public void mouseMoved(MouseEvent e){}

public void mousePressed(MouseEvent e)
{
    int x =e.getX();
    int y =e.getY();

    mandelRect.setXY (x, y);
}

public void mouseDragged(MouseEvent e)
{
    int x =e.getX();
    int y =e.getY();

    mandelRect.setWidthHeight (x, y);
    mandelRect.setPaintRect (true);
    repaint ();

}
/**
 * reorder the images, depending on which button is pressed
 * @param evt - event object
 * @param arg - target object
 */
public void actionPerformed(ActionEvent evt)
{
    Object object1 = evt.getSource();

    if (object1 == startButton) {
        mandelRect = new MandelRect (mWidth, mHeight);
        startCalculate = true;
        repaint ();
    }
    if (object1 == zoomButton)
    {
        startCalculate = true;
        mandelRect.setPaintRect (false);
        mandelRect.scaleSet ();
        repaint ();
    }
}

/**
 * application entry point
 * create window and new set
 * @param args - command-line arguments
 */
public static void main (String args[]) {

    Frame f = new Frame ("Mandelbrot set");
    Mandelbrot mandel = new Mandelbrot ();

    mandel.init ();
    f.setSize (210, 275);
    f.add ("Center", mandel);
    f.show ();
    f.addWindowListener(new WindowCloser());

    mandel.start ();
}
}

class WindowCloser extends WindowAdapter
{
    public void windowClosing(WindowEvent e)
    {
        Window win = e.getWindow();
        win.setVisible(false);
        win.dispose();
        System.exit(0);
    }
}