[Building Sakai] Images in public portfolios

[t.sanders at dgsvisueel.nl]

Images in public portfolios do not display using normal url's and force
anonymous viewers to log in (which they ususally can't). SAK-16203 is about
this. It is marked as fixed, but I am unable to get it to work. 

The suggested solution is to decorate the url with

"ospPresentation/<siteId>/<presentationId>/metaobjContent/<siteId>/<formUuid>"

and use  sakaifn:getReferenceUrl(URL, decoration) to get the final url
which should be accessible for anonymous users. As mentoined: I cannot get
this to work.
I have posted a comprehensive description of the problem on
https://jira.sakaiproject.org/browse/SAK-16203, please read the details
there. Any help/suggestion with this is highly appreciated. Thanks!

Tom