Paperclip attachment settings for width / height and thumbnail determination

paperclip

# contains common attachment methods
# NOTE: this currently assumes the attachment is called 'attachment'
module Attachable

  # determines if an attachment may have a thumbnail
  def thumbnailable?
    !(attachment_content_type =~ %r{^(image|(x-)?application)/(bmp|gif|jpeg|jpg|pjpeg|png|x-png|pdf)$}).nil?
  end

  def image_dimensions(max=400)
    return [0,0] unless thumbnailable?
    d = self.dimensions.max
    return self.dimensions if d <= max
    self.dimensions.map{|e| (max.to_f / d * e).to_i}
  end

  # Retrieves dimensions for image assets
  # @note Do this after resize operations to account for auto-orientation.
  def extract_image_dimensions
    return unless thumbnailable?
    tempfile = attachment.queued_for_write[:original]
    unless tempfile.nil?
      geometry = Paperclip::Geometry.from_file(tempfile)
      self.dimensions = [geometry.width.to_i, geometry.height.to_i]
    end
  end
end