nextcloud/apps/files_imageviewer/js/lightbox.js

$(document).ready(function() {
	if(typeof FileActions!=='undefined'){
		FileActions.register('image','View', FileActions.PERMISSION_READ, '',function(filename){
			viewImage($('#dir').val(),filename);
		});
		FileActions.setDefault('image','View');
	}
	OC.search.customResults.Images=function(row,item){
		var image=item.link.substr(item.link.indexOf('?file=')+6);
		var a=row.find('a');
		a.attr('href','#');
		a.click(function(){
			var pos=image.lastIndexOf('/')
			var file=image.substr(pos + 1);
			var dir=image.substr(0,pos);
			viewImage(dir,file);
		});
	}
});

function viewImage(dir, file) {
	if(file.indexOf('.psd')>0){//can't view those
		return;
	}
	var location=OC.filePath('files','ajax','download.php')+encodeURIComponent('?files='+encodeURIComponent(file)+'&dir='+encodeURIComponent(dir));
	$.fancybox({
		"href": location,
		"title": file.replace(/</, "&lt;").replace(/>/, "&gt;"),
		"titlePosition": "inside"
	});
}