One thing I thought is make the the strip a configuration option passed to the thumbnail method.. and then image_fu can be configurable too. I'd consider changing the API to:

```ruby
def thumbnail(options = {})
  options = {:geometry => options} if options.is_a?(String) # AND deprecation warning here.
  options = {:geometry => nil, :strip => true}.merge(options)

  # ...
end
```