/*
 * iterated interleavers
 */

import java.awt.*;

public class IteratedLinear extends java.applet.Applet {

	 int a = 1;
	 int b = 1;
	 int c = 1;
	 int d = 2;

	 public void init() {

	 }

  	 public void paint(Graphics g) {
		  int[] xy = new int[2];
		  int[] zw = new int[2];
		  for (int t = 0; t < 6; t++) {	// do t iterations of map
				g.setColor(Color.red);
				for (int i=0; i<50; i++) {       // upper left 1/5 x 1/5
					 for (int j=0; j<50; j++) {
						  xy[0] = i;
						  xy[1] = j;
						  zw = f(xy, t);
						  g.fillRect(t*150+zw[0],zw[1],1,1);
					 }
				}
				g.setColor(Color.blue);
				for (int i=50; i<100; i++) {
					 for (int j=0; j<50; j++) {
						  xy[0] = i;
						  xy[1] = j;
						  zw = f(xy, t);
						  g.fillRect(t*150+zw[0],zw[1],1,1);
					 }
				}
				g.setColor(Color.green);
				for (int i=0; i<50; i++) {
					 for (int j=50; j<100; j++) {
						  xy[0] = i;
						  xy[1] = j;
						  zw = f(xy, t);
						  g.fillRect(t*150+zw[0],zw[1],1,1);
					 }
				}
				g.setColor(Color.black);
				g.drawRect(150*t,0,150,150);
		  }
  	 }

	 int[] f( int[] xy ) {
		  // 149 is prime...
		  int[] out = new int[2];
		  out[0] = (a*xy[0]+b*xy[1]) % 149;
		  out[1] = (c*xy[0]+d*xy[1]) % 149;
		  return out;
	 }

	 int[] f( int[] xy, int t ) {
		  int[] out = new int[2];
		  out[0] = xy[0];
		  out[1] = xy[1];
		  if (t>0) {
				for (int i=0; i<t; i++) {
					 out = f(out);
				}
		  }
		  return out;
	 }
	 

}

/**********************************************************************/