#! perl -slw
use strict;
use GD;

our $X ||= 500;
our $Y ||= 500;

my $img = new GD::Image( 2*$X, $Y, 1 );
my $white = $img->colorAllocate( 255, 255, 255 );
my $black = $img->colorAllocate( 0, 0, 0 );
$img->filledRectangle( 0,0, $img->getBounds, $white );

## No anti-aliasing
for my $y ( map{ $_ * 20 } 0 .. $Y/ 20 ) {
    $img->line( 0, 0, $X, $y, $black );
}
for my $x ( map{ $_ * 20 } 0 .. $X/20 ) {
    $img->line( 0, 0, $x, $Y, $black );
}

## Same thing antialiased
$img->setAntiAliased( $black );
for my $y ( map{ $_ * 20 } 0 .. $Y/20 ) {
    $img->line( $X, 0, 2*$X, $y, gdAntiAliased );
}
for my $x ( map{ $_ * 20 } 0 .. $X/20 ) {
    $img->line( $X, 0, $X+$x, $Y, gdAntiAliased );
}

open PNG, '>:raw', 'test.png' or die $!;
print PNG $img->png( 9 );
close PNG;

system "test.png"; ## Adjust to start your favourite picture viewer.