file_column and ftp uploaded files

hi all!    i have a web application where the user can upload his files through FTP. It'done and it's ok. Now i want to let the user to select some ftp uploaded files and make them object in my application (they are images, so i like for example act_as_attachment plugin capabilities of making thumbnails automatically). I have strange errors, because i don't upload files, so my files havent' the variables (like original_filename) that an upload thourgh a form make appear.

Now my question: is it possibile to use act_as_attachment or file_column with "local" files on the server, not using a form to make the upload?

thanks,   nelson