Finding the Parameters of a Nonlinear Diffusion Denoising Method by Ridge Analysis

Abstract

Noise-suppression (denoising) methods depend on the parameters that regulate filtering intensity. The noise-free image is inaccessible in practice, and we have to choose optimal parameters that use only the original noisy image and a filtered image. Image quality can be measured in the presence of ridge structures (ridges and valleys) by analyzing difference frames. A method for filtering quality assessment is proposed: it evaluates the mutual information between the values of the difference frame points where ridge structures are present. Ridge structures are detected by analyzing the Hessian, which produces the directions and the characteristic width of the ridges and the valleys. The method has been tested for the Perona–Malik nonlinear diffusion on noisy images from the BSDS500 database.