$(document).ready( function() {
  $('div.gal-item a').colorbox({
        open: true,
        maxWidth: 600,
        maxHeight: 500,
        scalePhotos: true,
        slideshow: true,
        rel: 'gallery',
        transition: 'elastic',
        slideshowSpeed: 5000,
        onClosed: function() { $('div.gal-item').show();},
        current: 'afbeelding {current} van {total}'
   });
});