Nonlinear filters for image sharpening and smoothing

Abstract

A general approach to the transform-magnitude-shaping-based image enhancement method is advanced. In the method, the magnitude of the input image transform is modified using a nonlinear mapping expressible as a power series, while its phase is kept invariant. The inverse transform of the modified image transform results in a sharpening or smoothing depending on the choice of the power series coefficients. Further improvement in the overall enhancement is achieved by a two-channel processing scheme which is implemented by applying different transform amplitude shaping methods to the low-frequency and high-frequency components. Examples the proposed enhancement method are included.<>