#! perl -slw
use strict;
use GD;
use List::Util qw[ sum ];

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

## Gen some data
my %counts;
++$counts{ int( rand( 5e3 ) + rand( 5e3 ) ) } for 1 .. 1e6;
my @keys = sort{ $a <=> $b } keys %counts;

my $gd = GD::Image->new( 10000, 2000, 1 );

for my $step ( reverse 1.. 10 ) {
    my $start = 0;
    my $last = 0;
    my $clr = 2**24 / $step;

    for( my $end = $start+$step-1; $end < $keys[ -1 ]; $end += $step ) {

        my $sum = sum( @counts{ grep( defined $counts{ $_ }, $start..$end ) } ) // 0;
#        printf "%4d - %4d : %d\n", $start, $end, $sum;

        $gd->line( $start, 2000-$last, $end, 2000-$sum, $clr ) if $last;
        $start = $end + 1;
        $last = $sum;
    }
}

open IMG, '>:raw', 'junk14.png' or die $!;
print IMG $gd->png;
close IMG;

## Display the graph in the default image viewer
system 'junk14.png';