# File lib/pdf/reader/page_state.rb, line 55
      def concatenate_matrix(a, b, c, d, e, f)
        transform = Matrix[
          [a, b, 0],
          [c, d, 0],
          [e, f, 1]
        ]
        if state[:ctm]
          state[:ctm] = transform * state[:ctm]
        else
          state[:ctm] = transform
        end
      end