[Plugin: NextGEN Gallery] How to Link to Images Outside of Public HTML Folder

I’d like to know how to point a gallery to images outside of my public_html directory so that images can be displayed but not directly linked to.

I’ve tried entering a path for the gallery using ../../gallery syntax but the plug-in doesn’t recognize this as telling it to go back a few directories.

http://wordpress.org/extend/plugins/nextgen-gallery/