Rotating Images with file_column

Hi everyone, I have a photo site that I'm making and I'm using file_column to handle the auto-generation of several "version" of each photo: essentially thumbs and fuller-sized version. The full sized versions retain the original's proportions, whereas the thumbs are all 4:3. This means most of the thumbs are cropping the original. This all works great, but I want to let the user rotate the image after it has been uploaded and "processed".

This means I can simply rotate all the normal versions directly, but the thumbs will have to be regenerated. How can I trigger file_columm's auto-generation function without "reuploading" the image? Or better yet: is there a clean way to represent the image "versions" (which would consist of dimensions and cropping) which I can plug into the file_column and RMagick?

file_column :image, :store_dir => :photo_store_dir, :magick => {     :versions => {       :small_thumb => { :crop => '1:1', :size => '40x40>' },       :large_thumb => { :crop => '4:3', :size => '100x75>' },       :small => { :size => '640x480>' },       :medium => { :size => '800x600>' },       :large => { :size => '1024x768>' }     }   }

The above code works great. I just want to be able to use :small_thumb => { :crop => '1:1', :size => '40x40>' } in my RMagick code in order to regenerate my thumbs. Any ideas?

Thanks, Ryan