    # File lib/rubygame/gfx.rb, line 459
      def self.rotozoom_size( size, angle, zoom )
        w, h = size

        case zoom
        when Array
          zx, zy = zoom.collect { |n| n.to_f }
          SDL::Gfx.rotozoomSurfaceSizeXY(w, h, angle, zx, zy)
        when Numeric
          zoom = zoom.to_f
          SDL::Gfx.rotozoomSurfaceSize(w, h, angle, zoom)
        else
          raise ArgumentError, "Invalid zoom factor: #{zoom.inspect}"
        end
      end