def histogram_with_rgb( *ret_shape )
      if typecode < RGB_
        [ r, g, b ].histogram *ret_shape
      else
        histogram_without_rgb *ret_shape
      end
    end
def histogram_with_rgb( *ret_shape )
      if typecode < RGB_
        [ r, g, b ].histogram *ret_shape
      else
        histogram_without_rgb *ret_shape
      end
    end
Compute colour histogram of this array

 The array is decomposed to its colour channels and a histogram is computed.

 @overload histogram( *ret_shape, options = {} )
   @param [Array<Integer>] ret_shape Dimensions of resulting histogram.
   @option options [Node] :weight (Hornetseye::UINT(1)) Weights for computing the
           histogram.
   @option options [Boolean] :safe (true) Do a boundary check before creating the
           histogram.

 @return [Node] The histogram.