resize_to_fill image with sizes from model

uploader.rb

class CoverUploader < CarrierWave::Uploader::Base
  include CarrierWave::RMagick

  version :some_vesion do
    process :do_resize
  end


  def do_resize
    manipulate! do |img|
      sizes = model.cover_type.split('x').map { |t| t.to_i }
      img.resize_to_fill(sizes[0], sizes[1])
    end
  end
end