Fingerprint Orientation Field Interpolation Based on the Constrained Delaunay Triangulation

A direction map or an orientation field is widely used in automatic fingerprint verification and recognition systems. In most existing methods, the block-wise orientation field is computed from the squared gradients. Since a fingerprint image can contain areas that may be smeared or scarcely distributed, faulty orientations can be produced during the process of orientation field estimation. In this paper, we propose a constrained Delaunay triangulation (CDT) based orientation field interpolation method. In this method, the orientation coherence is used to segment an image into foreground and background, valid regions and invalid regions, and the contours of the invalid regions are used to construct the CDT that is used to interpolate the orientations of the invalid regions. Compared with the commonly used filter and diffusion based methods, the advantages of our method include that no pre-defined neighborhood is needed, that no iteration is needed, and that the orientations still conform well to the fingerprints’ ridges and valleys. Our experiment results show the efficiency of the proposed approach.