tillid

Sure! This will work to add a button in de gallery under the image (So not in the lightbox). I also did not try to make a download button for all images yet.

var src = $('#fancybox-content img').attr('src');
	$("<a href='" + src +"'>Download image</a>").appendTo("#fancybox-content");

	$('.ngg-gallery-thumbnail').each(function() {
		var src = $(this).find('a').attr('href');
		$("<div class='downloadFoto'><a href='" + src +"' download>Download deze foto</a></div>").appendTo(this);
	});