baclight/app/models/id_card/employer_logo.rb

module IdCard
  class EmployerLogo < ApplicationRecord
    before_validation :calculate_aspect_ratio, if: :image_data_changed?

    private

    def calculate_aspect_ratio
      image_io = StringIO.new(self.image_data)
      width, height = FastImage.size(image_io)
      image_ratio = width.to_f / height
      if image_ratio
        self.aspect_ratio = image_ratio.round(2)
      end
    end
  end
end