// Simple Java Applet to generate a black and white Mandelbrot set
// Written by phgod on 20050721

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

public class bwMandelbrot extends Applet {

  int width, height;

  public void init() {
    // The calling HTML determines the size
    width = getSize().width;
    height = getSize().height;
    setBackground( Color.white );
  }

  public void paint(Graphics g) {

    final int a_MIN=1, a_MAX=width-2, b_MIN=1, b_MAX=height-2;
    final int da=1, db=1;

    // The bounding box
    g.setColor(Color.black);
    g.drawRoundRect(a_MIN, b_MIN, a_MAX, b_MAX, 15, 15);

    for(int ia=a_MIN; ia<a_MAX; ia+=da){
      for(int ib=b_MIN; ib<b_MAX; ib+=db){
        if(IsFinite(3.*(ia-a_MIN)/(a_MAX-a_MIN)-2., 2.*(ib-b_MIN)/(b_MAX-b_MIN)-1.)){
          g.fillOval(ia, ib, 2, 2);
        }
      }
    }

    // Print the title
    g.setColor( Color.red );
    g.drawString( "Mandelbrot set in Java applet", 10, 20);

  }

  // A point should be drawn if the iteration does not diverge.
  // Draw the point if this function returns true.
  private boolean IsFinite(double a, double b){
    final int N_TEST=200;
    double x=0, y=0, oldx, oldy;
    for(int nTest=0; nTest<N_TEST; nTest++){
      oldx=x;	oldy=y; 
      // Iteration: z = (z0)^2 + (a+bi)
      x=oldx*oldx-oldy*oldy+a;
      y=2*oldx*oldy+b;
      // Regard as divergence if |z|>2
      if(x*x+y*y>4) return false;
    }
    return true;
  }


}