Generalized explicit schemes for coherence-enhancing diffusion filtering

This paper presents generalized explicit schemes (GESs) for coherence-enhancing diffusion (CED) filtering, which is one of a wide variety of nonlinear diffusion filtering schemes. Unlike the traditional standard explicit scheme, which updates the diffusion coefficients in each iteration, the generalized ones use several new updating types, including fixed diffusion coefficients and the uniform-interval update (UIU) and optimized interval update (OIU) of diffusion coefficients. The GESs significantly improve efficiency by reducing the computational cost of updating the diffusion coefficients, compared with the existing acceleration methods, and by enlarging the time step, as in implicit or semi-implicit schemes or a scheme with larger mask of spatial discretization. Also, the OIU may allow the GES to achieve high accuracy by using only two to four updates of the diffusion coefficients during the whole process. Experiments demonstrate that the efficiency of the GESs is comparable to those of existing acceleration methods; nevertheless, the GESs with the OIU outperforms the other methods in the efficiency-accuracy trade-off. (C) 2008 Society of Photo-Optical Instrumentation Engineers.