Using render within plugin


I am very, very new to rails (and ruby) and am working on a view
extension helper method. In a template I have
<%= my_helper params %>

my_helper does some system calls and ends up placing an image file in
the public images folder (which I referenced within the plugin using
RAILS_ROOT). I want the helper to then return an appropriate image link
to the template. I want to use the image_tag method to do so, or at
least render that within an inline template, but I don’t know how to get
the active controller to do so. Thanks for any help.