INTERFACE PhiFeatures2D;
(*
  A feature mapper that computes the five "phi" invariants, from
  the pixel and its 8 nearest neighbors. 
  Each image layer generates 5 consecutive features. *)

IMPORT FeatureMapper2D AS Mapper;
FROM Mapper IMPORT NAT;

TYPE
  T <: Public;
  Public = Mapper.T OBJECT METHODS
      init(NL: NAT): T; (* Initializes the mapper for "NL" layers. *)
    END;

END PhiFeatures2D.