# File lib/action_view/helpers/asset_tag_helper.rb, line 628
      def image_tag(source, options = {})
        options.symbolize_keys!

        src = options[:src] = path_to_image(source)

        unless src =~ /^cid:/
          options[:alt] = options.fetch(:alt){ File.basename(src, '.*').capitalize }
        end

        if size = options.delete(:size)
          options[:width], options[:height] = size.split("x") if size =~ %r{^\d+x\d+$}
        end

        if mouseover = options.delete(:mouseover)
          options[:onmouseover] = "this.src='#{path_to_image(mouseover)}'"
          options[:onmouseout]  = "this.src='#{src}'"
        end

        tag("img", options)
      end