ABSTRACT
This chapter suggests that process by exploring frequency-based filters. The Fourier transforms organizes the information so that an element in the output array is the intensity of a particular frequency component. The low-pass filter will block the high frequencies and all the low frequencies to pass through the filter. Since the low frequencies are collected near the center of the frame after a swap operation, the low-pass filter is easy to create. The high-pass filter is just the opposite of a low-pass filter, as the masks are the complements of the other. The high-pass filter allows the high frequencies to survive and blocks the low frequencies. A wedge filter is so named because the filter is a set of opposing wedges centered in the frame. Fingerprint images are interesting in that they consist of lines and flow rather than large contiguous objects. Algorithms that sort the prints into groups rely heavily on the analysis of these flow patterns.
