attachment_fu, minimum width and height, how?

There are hooks for after create and after save (and update,
destroy...etc)

just implement a method that is called after_create and put your
validation there, you can revert chanegs if your size is incorrect.
There is another way. validations in models allow the :on key like
validate :correct_size :on => :create

def correct-size
  errors.add...
end

i might be completely on another topic though :slight_smile: