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Abstract

A fingerprint identification system from a gray scale image of the fingerprint includes the steps of converting fingerprint image into a digitized gray scale image, enhancing gray scale to provide uniform contrast over entire fingerprint image, down-sampling the contrast enhanced image to limit the number of pixels analyzed, generating a gradient map of the fingerprint image, defining a calculation kernel over which ridge angle determination is made by reference to gradient map, causing the calculation kernel to traverse over gradient map in a predetermined increment over pixels comprising the fingerprint image, smoothing the ridge angle map using the process of Fourier filtering, and smoothing the image quality map using the process of erosion and dilation. The ridge angle map and image quality maps are recorded. The frequency of ridges of a fingerprint image is determined by establishing at each selected pixel a line perpendicular to ridge flow, establishing a plurality of lines parallel to perpendicular line placed on both sides of perpendicular line of selected pixel, sampling a predetermined number of pixels along the perpendicular lines, averaging sample of each line, determining frequency of ridges by calculating power spectrum from a Fourier transform.

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First Claim