validates :width, :presence => true, :numericality => true, :natural_number => true
validates :height, :presence => true, :numericality => true, :natural_number => true
validates :border, :presence => true, :numericality => {:greater_than_or_equal_to => 0}
validates :width, :presence => true, :numericality => true, :natural_number => true
validates :height, :presence => true, :numericality => true, :natural_number => true
validates :border, :presence => true, :numericality => {:greater_than_or_equal_to => 0}