Screen Capture / Saving CSS3 to image somehow?

I have a div that's 512x512 and th开发者_如何转开发e user can drag/drop stuff around.

I would like to save this for use in an email which doesn't support many CSS properties.

My initial idea was to take a screenshot and crop it but I can't seem to find a good way of doing this.

I figured out how to do this and wrote a blog post on it here - http://jbeas.com/ruby-on-rails/rails-screenshot-pdf-gem/