# File lib/bio/graphics/page.rb, line 222
      def get_limits
        @tracks.each do |track|
          lowest = track.features.sort { |x, y| x.start <=> y.start }.first.start
          highest = track.features.sort { |x, y| y.end <=> x.end }.first.end
          @scale_start = lowest if lowest < @scale_start
          @scale_stop = highest if highest > @scale_stop
          @nt_per_px_x = (@scale_stop - @scale_start).to_f / @width.to_f
        end
      end