1. A method of processing a skin print image, and particularly a fingerprint image, which image exists as a gray-level image, comprising a processor for performing the steps of: convolving the gray-level image in the direction of two axes (x, y) by generalized gradient filters, wherein the generalized radiant filters each constitute the superimposition of a two-dimensional Gaussian bell curve and a suitably enlarged radiant filter, the size of each of which is adjusted to suit the average density of the furrows in the skin print image; normalizing the generalized gradients, convolving each of the normalized, generalized gradients with said generalized gradient filters, summing results of the convolution of the normalized, generalized gradients; and converting the results of the convoluted, normalized, generalized gradients to binary form.