Paperclip Validate minimum image dimensions

paperclip_image_dimensions_validation.rb

validate :check_dimensions

def check_dimensions
  temp_file = background_image.queued_for_write[:original]
  unless temp_file.nil?
    dimensions = Paperclip::Geometry.from_file(temp_file)
    width = dimensions.width
    height = dimensions.height
    
    if width < 800 && height < 600
      errors[''] << " dimensions are too small. For a good quality background please upload a larger image. Minimum width: 800px, minimum height: 600px"
    end
  end
end