Rails 3.1.0 how to pass the full url of an image asset?

I need to reference the full url of an image stored in the assets,
this url is passed to fancy box to open it

I build the image path in helper and it get the path
“ceramics/big/c0d0.jpg” “ceramics/big/c0d2.jpg”, …

but I need to get the full url to these image

asset_path(“ceramiques/big/c0d0.jpg”) => “/assets/ceramiques/big/

but there is no asset_url to get
or http://www.mydomain.com/assets/ceramiques/big/c0d0.jpg

thanks for your feedback

Something like this should do the trick. You can just add this as a

def asset_url(source)