def lut_with_rgb( table, options = {} )
      if typecode < RGB_
        [ r, g, b ].lut table, options
      else
        lut_without_rgb table, options
      end
    end
def lut_with_rgb( table, options = {} )
      if typecode < RGB_
        [ r, g, b ].lut table, options
      else
        lut_without_rgb table, options
      end
    end
Perform element-wise lookup with colour values

 @param [Node] table The lookup table (LUT).
 @option options [Boolean] :safe (true) Do a boundary check before creating the
         element-wise lookup.

 @return [Node] The result of the lookup operation.