Fingerprint directional image/field is a key technique of automated fingerprint identification system (AFIS). In order to improve the accuracy of fingerprint directional image further

combining the advantage of the continuity of the point directional image with the advantage of the robustness of the block directional image to the noises in the fingerprint image

a novel concept on the continuously distributed directional image/field (CDDF) and the method to compute it in the fingerprint images are developed

which transits smoothly and exhibits not only good continuity

well gradualness and excellent robustness to the noises

but very high precision

also. Therefore

it can effectively overcome the defect of low robustness to the noises of the point directional image and the weakness of low precision of the block directional image of the fingerprint image. The experimental results prove that the continuously distributed directional image can not only filter the noises in point directional image

but also represent the basic structural feature of fingerprint more precisely. Furthermore

it can solve the key problem of the continuity

the precision and the performance of robustness of fingerprint directional fields effectively

and lays the base for high precision of fingerprint image enhancement

binarization

global feature extraction

automatic classification

template matching and image encoding in AFIS.