Mandelbrot p3 processing

class Complex
{
  float a, b;
  Complex(float r, float c)
  {
    a=r;
    b=c;
  }
  Complex()
  {
    a=0;
    b=0;
  }
  Complex mult(Complex c)
  {
    float newR=a*c.a-b*c.b;
    float newC=a*c.b+b*c.a;
    return new Complex(newR, newC);
  }
  Complex add(Complex c)
  {
    float newR=a+c.a;
    float newC=b+c.b;
    return new Complex(newR, newC);
  }
  float mag()
  {
    return pow(a*a+b*b, .5);
  }
  String toString()
  {
    return a+" + "+b+"i";
  }
}
Complex zero=new Complex(), c, z=new Complex();
int val;
float a, b, x=0, y=0;
float cX=0, cY=0, rad=2, inc=.1, oldRad=2;
float prevX=0, prevY=0;
void setup()
{
  background(0);
  strokeWeight(1);
  size(2000, 2000, P2D);
  colorMode(HSB);
  noLoop();
  fill(0);
}
void draw()
{
  rect(0, 0, width, height);
  for (int t=0; t<width*height; t++)
  {
    a=2*oldRad*x/width-(oldRad-prevX);
    b=2*oldRad*y/height-(oldRad-prevY);
    c=new Complex(a, b);
    val=iterate();
    if (val!=256)
      stroke(val, 255, 255);
    else
      stroke(0, 0, 0);
    point(x, y);
    t++;
    x=t%width;
    y=t/height;
  }
  println("Done!");
}
int iterate()
{
  int i;
  z=zero;
  for (i=0; i<256&&z.mag()<2; i++)
    z=z.mult(z).add(c);
  return i;
}
void mousePressed()
{
  cX=2*oldRad*mouseX/width-(oldRad-prevX);
  cY=2*oldRad*mouseY/width-(oldRad-prevY);
  print("Center: ("+cX+", "+cY+")\n");
}
void keyPressed()
{
  inc=rad/10;
  if (key!=ENTER)
  {
    if (key=='+')
      rad+=inc;
    else if (key=='-')
      rad-=inc;
    else if(key=='0')
    {
      rad=2;
      cX=0;
      cY=0;
    }
    println("Radius: "+rad);
  }
  else
  {
    println("Drawing new set centered @ ("+cX+", "+cY+") with radius: "+rad);
    prevX=cX;
    prevY=cY;
    oldRad=rad;
    redraw();
  }
}