Topic: get content_type from a local file?

I'm using a Rake task to add local files into a database designed for use with attachment_fu.

http://eldorado.googlecode.com/svn/trun … avatars.rb
http://eldorado.googlecode.com/svn/trun … files.rake

So, attachment_fu has a "content_type" field, which apparently is receiving that information from the browser...?

I'm trying to figure out if there is a way to get the content_type of a file (e.g. 'image/png') that you've already got in your file-system. I can't find anything about this in the Pickaxe, or by looking at the attachment_fu plugin.

Any help very much appreciated!