US Patent 7502524 Method and apparatus of processing a skin print image

In a method and an arrangement for processing a skin print image, and particularly a fingerprint image, which image exists as a gray-level image, provision is made for the gray-level image to be convolved in the direction of two axes (x, y) by generalized gradient filters (Gx, Gy), for the generalized gradients (Bx, By) obtained in this way to be normalized, for the normalized, generalized gradients (Cx, Cy) each to be convolved with generalized gradient filters (Qx, Qy), and for the sum (D) of the two results (Dx, Dy) of the convolution of the normalized, generalized gradients (Cx, Cy) to be converted to binary form.