A new technique for image edge crisping based on rational function mapping

A new technique in the frequency domain for image edge crisping or enhancement is proposed. In this method, the Fourier transform magnitude of an image is modified by a rational function with the phase kept invariant. The inverse transform of the modified Fourier transform results in an enhanced image with edge crisping. In practical applications, the use of the method is shown to produce better results. The method is somewhat similar to the alpha-rooting method (W.K. Pratt, 1978) or the transform amplitude sharpening method (S.K. Mitra and T.H. Yu, 1987), but the new technique does not suffer from the serious side-effects of the alpha-rooting method and is more effective and simpler than the transform amplitude sharpening method.<>