#! perl -slw
use strict;
use GD;

sub rgb2n { unpack 'N', pack 'CCCC', 0, @_ }

my @heights = map [
    map int rand 256, 1 .. 500
], 1 .. 500;

my $img = GD::Image->new( 500, 500, 1 );

for my $y ( 0 .. $#heights ) {
    for my $x ( 0 .. $#{ $heights[ $y ] } ) {
        $img->setPixel( $x, $y, rgb2n( ( $heights[ $x][ $y ] ) x 3 ) );
    }
}

binmode STDOUT;
print $img->png;