def add_image(options={})
      if options[:end_at]
        TwoCellAnchor.new(self, options).add_pic(options)
      else
        OneCellAnchor.new(self, options)
      end
      @anchors.last.object
    end
Adds an image to the chart If th end_at option is specified we create a two cell anchor. By default we use a one cell anchor.
@note The recommended way to manage images is to use Worksheet.add_image. Please refer to that method for documentation.
@see Worksheet#add_image
@return [Pic]