application_helper.rb

module ApplicationHelper
  def placeholdit(geometry, options = {})
    base = "http://placehold.it/"

    additional_options = []

    if geometry =~ /\A\d+(x\d+)?\z/
      additional_options << geometry
    else
      additional_options << 200
    end

    additional_options << options[:bg]
    additional_options << options[:fg]

    base << additional_options.compact.join("/")

    if (text = options[:text]).present?
      text.gsub!(/&|#/, "")
      base += "&text=#{CGI.escape(text)}"
    end

    image_tag base
  end
end