$driver->set_window_size(320, 480);
    $elem = $driver->find_element('applgs','id' ); 
    my $white = Selenium::Screenshot->new(
                   png => $driver->screenshot,
                   exclude => [{
                     size     => { width => 10, height => 10 }, 
                     location => { x => 5, y => 5 }, 
      }]
    )->save( file => "snapScreenshot" );
    $driver->execute_script('document.getElementsByTagName("body")[0].style.backgroundColor = "red"');
    my $blue = Selenium::Screenshot->new(png => $driver->screenshot)->save( file => "snapScreenshot1" );

    unless ($white->compare($blue)) {
      my $diff_file = $white->difference($blue);
      print 'The images differ; see ' . $diff_file . ' for details';
    }