a method to extract automatic high level features of a gray level ridge flow image including the automatic determination of the location of the high level features including the core and delta points of a fingerprint image in the form of a gray level image , comprising the following five steps : determining a ridge flow direction of each gray level pixel of a fingerprint image and assign it with a direction code ; finding out a block directional flow and assigning each with appropriate direction code thereof ; correcting block flow directions in which a detection of the flow direction is affected image an input image quality in order to be immune from noises infiltrated during the acquiring process ; locating the delta points which are based on a corrected block direction flow diagram to locate from zero to a few delta points ; and locating the core points which are based on a corrected block direction flow diagram to locate one to two core points .