deliver attachment in show function?

[Jan Prieser]

Hi,

is it possible to deliver an attachment through a show function?
i've tried this with no success:
GET 
/images/_design/images/_show/onlineimage/a0cbe43b55828d33320cf6cbd40bdb81?attachments=true

function (doc, req) {
        if (doc.type == "image" && doc.online == "online") {
                return {
                        body: doc._attachments["filename"].data,
                        headers: { "content-type" : 
doc._attachments["filename"].content_type}
        
                }
        }
        else {
                return 'not found or offline';
        }
}

Reason is to rewrite this URL in varnish cache and only deliver images 
which are flagged online in doc.online.
My application would ask for http://varnish/image/<imagedocid> and only 
get online images.
I'm trying to avoid an extra http roundtrip through the application server.

any ideas how to accomplish this scenario?

regards,
jan prieser