A Hybrid Fingerprint Enhancement Algorithm

1 The author was supported in part by NSC grant 94-2213-E-033-031. 2 The author was supported in part by NSC grant 94-2213-E-033-024. Abstract Fingerprint image enhancement is a common and critical step in fingerprint recognition systems. To enhance the images, most of the existing enhancement algorithms use filtering techniques that can be categorized into isotropic and anisotropic according to the filter kernel. Isotropic filtering can properly preserve features on the input images but can hardly improve the quality of the images. On the other hand, anisotropic filtering can effectively remove noises from the image but only when a reliable orientation is provided. In this paper, we propose an orientation estimation and verification algorithm which can not only generate an orientation of ridge flows, but also verify its reliability. Based on this algorithm, a hybrid fingerprint enhancement algorithm is developed which applies isotropic filtering on regions without reliable orientations and anisotropic filtering on regions with reliable orientations. Experimental results show the proposed algorithm can combine advantages of both isotropic and anisotropic filtering techniques and generally improve the quality of fingerprint images.