Thanks Choroba ! It works right now . But i have another issue. Why i could not have a black out in my page. It should work :

    $elem = $driver->find_element('applgs','id' );
    my $white = 'Selenium::Screenshot'->new(
                   png => $driver->screenshot,
                   exclude => [{
                     size     => { width => 10, height => 10 }, #  siz
+e      => $elem->get_size,
                     location => { x => 5, y => 5 }, #location  => $el
+em->get_element_location,
      }]
    );
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