[Zope] call an object from within a product

Hi there, my question is probably quite stupid, but I can't find the answer anywhere: how to call an object from a product? I would like to obtain exactly the same result as if the object was called through the web or with dtml-var. I wrote something like: #get the object object = self.unrestrictedTraverse(url) try: #Call the object as a DTML method htmlsource = localObject.__call__(object, REQUEST) except: #Call the object as a folder htmlsource = localObject.index_html.__call__(object, REQUEST) This works for folders and DTML Methods, but not for images... I would like to let ZPublisher do the work for me!