draw_bars (Gruff::Bar)

    # File lib/gruff/bar.rb, line 20
      def draw_bars
        # Setup spacing.
        #
        # Columns sit side-by-side.
        spacing_factor = 0.9 # space between the bars
        @bar_width = @graph_width / (@column_count * @data.length).to_f

        @d = @d.stroke_opacity 0.0

        # Setup the BarConversion Object
        conversion = Gruff::BarConversion.new()
        conversion.graph_height = @graph_height
        conversion.graph_top = @graph_top

        # Set up the right mode [1,2,3] see BarConversion for further explanation
        if @minimum_value >= 0 then
          # all bars go from zero to positiv
          conversion.mode = 1
        else
          # all bars go from 0 to negativ
          if @maximum_value <= 0 then
            conversion.mode = 2
          else
            # bars either go from zero to negativ or to positiv
            conversion.mode = 3
            conversion.spread = @spread
            conversion.minimum_value = @minimum_value
            conversion.zero = -@minimum_value/@spread
          end
        end

        # iterate over all normalised data
        @norm_data.each_with_index do |data_row, row_index|

          data_row[DATA_VALUES_INDEX].each_with_index do |data_point, point_index|
            # Use incremented x and scaled y
            # x
            left_x = @graph_left + (@bar_width * (row_index + point_index + ((@data.length - 1) * point_index)))
            right_x = left_x + @bar_width * spacing_factor
            # y
            conv = []
            conversion.getLeftYRightYscaled( data_point, conv )

            # create new bar
            @d = @d.fill data_row[DATA_COLOR_INDEX]
            @d = @d.rectangle(left_x, conv[0], right_x, conv[1])

            # Calculate center based on bar_width and current row
            label_center = @graph_left +
                          (@data.length * @bar_width * point_index) +
                          (@data.length * @bar_width / 2.0)
            # Subtract half a bar width to center left if requested
            draw_label(label_center - (@center_labels_over_point ? @bar_width / 2.0 : 0.0), point_index)
          end

        end

        # Draw the last label if requested
        draw_label(@graph_right, @column_count) if @center_labels_over_point

        @d.draw(@base_image)
      end