On the fly thumbnail generation

Hi & a very Happy Christmas everyone!

file_column trunk lets me do something wonderful: it can generate image thumbnails on the fly. Need a new thumbnail size? Just pass the new size to file_column's helper, and it'll automatically generate (and cache) a new thumbnail.

This is wonderful, wonderful stuff, and I'm surprised that most (all?) of the other file uploading plugins don't seem to support this, only letting me generate thumbnails at the time the image is uploaded. When you have a site with thousands of users and tens of thousands of uploaded images, and you suddenly need a new thumbnail size, the last thing you'd want to do is having to manually (through script or monkeys) generate new thumbnails for all existing images.

So, this really is a request rather than a question. Dear file upload plugin authors, please support this in your plugins. It's A Good Idea.

(Or tell me how blind and stupid I am, in case your plugins already do this and I just couldn't see it.)

Thanks!

- Hendrik