/* Orbits.java - A Java applet to display orbits of complex numbers under iteration of the qudratic map
 *  Author: Barry Tolnas
 *  Created: 5/11/2005
 */
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.*;
import javax.swing.*;
import javax.swing.event.*;

public class Orbits extends JApplet {
    final int iterations=255;
    final double centerR = -.5;
    final double centerI = 0;

    int width,height;
    double scale;

    BufferedImage map;
    GeneralPath orbit = new GeneralPath();
    
    public void init() {
 
        //Create a colormap which contains a gradient
        //  of grey values from black to white
	byte[] red   = new byte[256];
	byte[] green = new byte[256];
	byte[] blue  = new byte[256];
        for (int i=0;i<256;i++) red[i]=green[i]=blue[i]=(byte)(256-i);
	red[1]=0; green[1]=0; blue[1]=0;
        IndexColorModel colormap = new IndexColorModel(8,256,red,green,blue);

	width=this.getWidth();
	height=this.getHeight();
	map = new BufferedImage(width,height,BufferedImage.TYPE_BYTE_INDEXED,colormap);
	renderMandelbrot(map);

	OrbitListener listener = new OrbitListener();
	addMouseListener(listener);
	addMouseMotionListener(listener);
	addComponentListener(new ResizeListener());
    }

    public void paint(Graphics g) {
	Graphics2D g2 = (Graphics2D) g;
	g.drawImage(map,0,0,this);
	g2.setColor(Color.red);
	g2.draw(orbit);
    }

    public void renderMandelbrot(BufferedImage image) {
	width = image.getWidth();
	height= image.getHeight();
        scale   = 3.0/height;

	int[] im = new int[width*height];

	double x,y,value;
	for(int py=0;py<height;py++) {
	    for(int px=0;px<width;px++) {
		x = (px -  width/2)*scale + centerR;
		y = (height/2 - py)*scale + centerI;
		value = Mandelbrot(x,y);
		im[px+py*width] = (byte)value;
	    }
	}

	setImage(im,map);
	this.repaint();
	System.out.println("Done.");
    }

    private double Mandelbrot(double real, double imaginary) {
	int iters=0;
	double a=0, b=0;
	double newa=0;
	while ((a*a+b*b < 4) && (iters<iterations)) {
	    newa=a*a-b*b+real;
	    b=2*a*b+imaginary;
	    a=newa;
	    iters++;
	}
	return iters;
    }

    protected void setImage(int[] imageArray, BufferedImage image) {
        //only do this if the imageArray is the right length
        if (imageArray.length==width*height) {
	    WritableRaster raster=image.getRaster();
	    raster.setPixels(0,0,width,height,imageArray);
	}
    }

    private class OrbitListener extends MouseInputAdapter {
	public void mouseMoved(MouseEvent e) {
	    orbit = new GeneralPath();
	    int x = e.getX();
	    int y = e.getY();
	    orbit.moveTo(x,y);
	    
	    double real = (x-width/2)*scale + centerR;
	    double imaginary = (height/2 - y)*scale + centerI;

	    double a=0, b=0;
	    double newa=0;
	    int iters=0;
	    while ((a*a+b*b < 4) && (iters<iterations)) {
		newa=a*a-b*b+real;
		b=2*a*b+imaginary;
		a=newa;

		x=(int)(((a-centerR)/scale) + (width/2));
		y=(int)((height/2) - ((b-centerI)/scale));
		orbit.lineTo(x,y);
		iters++;
	    }
	    repaint();
	}
    }

    private class ResizeListener extends ComponentAdapter {
	public void componentResized(ComponentEvent e) {
	    width = getWidth();
	    height= getHeight();
	    init();
	}
    }

}