#! perl -slw
use strict;
use GD;

GD::Image->trueColor( 1 );

my $im1 = GD::Image->new( $ARGV[ 0 ] );
my $im2 = GD::Image->new( $ARGV[ 1 ] );

my $raw1 = $im1->gd;
my $raw2 = $im2->gd;

my $xored = $raw1 ^ $raw2;
my( $all, $diff ) = (0)x2;

$all += 255, $diff += ord substr $xored, $_, 1 for 0 .. length( $xored ) - 1;

print $all, ' ', $diff;

printf "The simlarity is %.3f%%\n", ( $all - $diff ) / $all * 100;