have you checked out this page: http://docs.rhomobile.com/rhodes/device-caps#file-system-access ? It looks to me like you need to save the image to the DB and use the Rho::RhoApplication::get_blob_path(image.image_uri) method to open the file. Then you should be able to use the file system API to create a new file and write the contents of the image to it wherever you choose.
