    # File lib/compass/sass_extensions/functions/urls.rb, line 51
      def image_url(path, only_path = Sass::Script::Bool.new(false), cache_buster = Sass::Script::Bool.new(true))
        path = path.value # get to the string value of the literal.

        if path =~ %r{^#{Regexp.escape(Compass.configuration.http_images_path)}/(.*)}
          # Treat root relative urls (without a protocol) like normal if they start with
          # the images path.
          path = $1
        elsif absolute_path?(path)
          # Short curcuit if they have provided an absolute url.
          return Sass::Script::String.new("url(#{path})")
        end

        # Compute the path to the image, either root relative or stylesheet relative
        # or nil if the http_images_path is not set in the configuration.
        http_images_path = if relative?
          compute_relative_path(Compass.configuration.images_path)
        elsif Compass.configuration.http_images_path
          Compass.configuration.http_images_path
        else
          Compass.configuration.http_root_relative(Compass.configuration.images_dir)
        end

        # Compute the real path to the image on the file stystem if the images_dir is set.
        real_path = if Compass.configuration.images_dir
          File.join(Compass.configuration.project_path, Compass.configuration.images_dir, path)
        end

        # prepend the path to the image if there's one
        if http_images_path
          http_images_path = "#{http_images_path}/" unless http_images_path[-1..-1] == "/"
          path = "#{http_images_path}#{path}"
        end

        # Compute the asset host unless in relative mode.
        asset_host = if !relative? && Compass.configuration.asset_host
          Compass.configuration.asset_host.call(path)
        end

        # Compute and append the cache buster if there is one.
        if cache_buster.to_bool
          if cache_buster.is_a?(Sass::Script::String)
            path += "?#{cache_buster.value}"
          else
            path = cache_busted_path(path, real_path)
          end
        end

        # prepend the asset host if there is one.
        path = "#{asset_host}#{'/' unless path[0..0] == "/"}#{path}" if asset_host

        if only_path.to_bool
          Sass::Script::String.new(clean_path(path))
        else
          clean_url(path)
        end
      end