# File lib/compass/grid_builder.rb, line 40
    def generate!
      return false unless self.able_to_generate
      total_width = self.column_width + self.gutter_width
      height = 20
      RVG::dpi = 100

      rvg = RVG.new((total_width.to_f/RVG::dpi).in, (height.to_f/RVG::dpi).in).viewbox(0, 0, total_width, height) do |canvas|
        canvas.background_fill = 'white'

        canvas.g do |column|
          column.rect(self.column_width, height).styles(:fill => "#e8effb")
        end

        canvas.g do |baseline|
          baseline.line(0, (height - 1), total_width, (height- 1)).styles(:fill => "#e9e9e9")
        end
      end

      filename = File.join(self.output_path, "grid.png")
      if File.exists?(filename)
        if options[:force]
          overwrite = true
        else
          msg = "#{filename} already exists. Overwrite with --force."
          raise Compass::FilesystemConflict.new(msg)
        end
      end
      directory self.output_path
      logger.record((overwrite ? :overwrite : :create), basename(filename))
      rvg.draw.write(filename)
    end