Hypnotic Rectangles

Hypnotic Rectangles

I made this picture with a little perl script

 #!/bin/perl
use GD;
 
$picture = new GD::Image(500,500); 
$white = $picture->colorAllocate(255,255,255); 
$black= $picture->colorAllocate(0,0,0); 
$deltax=-3;
for ($x=50;$x<=450;$x=$x+100)
{
    $deltax++;
    $deltay=-3;
    for ($y=50;$y<=450;$y=$y+100)
    {
        $deltay++;
        $deltaz=0;  
        for($z=48;$z>=4;$z=$z-4)
        {   
            $deltaz++;
            $deltaz++;      
            $picture->rectangle($x+$deltax*$deltaz-$z,$y+$deltay*$deltaz-$z,$x+$deltax*$deltaz+$z,$y+$deltay*$deltaz+$z,$black);
        }

    }
}
open(IMG, '>rectangles.gif') or die $!;              
binmode IMG;                                     
print IMG $picture->gif;                          
close(IMG);