Rapid Anisotropic Diffusion Using Space-Variant Vision

  • Authors:
  • Bruce Fischl;Michael A. Cohen;Eric L. Schwartz

  • Affiliations:
  • Department of Cognitive and Neural Systems, Boston University, Boston, MA 02215. E-mail: fischl@cns.bu.edu, mike@cns.bu.edu, eric@thing4.bu.edu;Department of Cognitive and Neural Systems, Boston University, Boston, MA 02215. E-mail: fischl@cns.bu.edu, mike@cns.bu.edu, eric@thing4.bu.edu;Department of Cognitive and Neural Systems, Boston University, Boston, MA 02215. E-mail: fischl@cns.bu.edu, mike@cns.bu.edu, eric@thing4.bu.edu

  • Venue:
  • International Journal of Computer Vision
  • Year:
  • 1998

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Abstract

Many computer and robot vision applications requiremulti-scale image analysis. Classically, this has been accomplishedthrough the use of a linear scale-space, which is constructed byconvolution of visual input with Gaussian kernels of varying size(scale). This has been shown to be equivalent to the solution of a linear diffusion equation on an infinite domain, as the Gaussian isthe Green‘s function of such a system (Koenderink, 1984).Recently, much work has been focused on the use of a variableconductance function resulting in anisotropic diffusion described bya nonlinear partial differential equation (PDE). The use of anisotropic diffusion with a conductance coefficient which is adecreasing function of the gradient magnitude has been shown toenhance edges, while decreasing some types of noise (Perona andMalik, 1987). Unfortunately, the solution of the anisotropicdiffusion equation requires the numerical integration of a nonlinear PDE which is a costly process when carried out on a uniform mesh suchas a typical image. In this paper we show that the complex logtransformation, variants of which are universally used in mammalianretino-cortical systems, allows the nonlinear diffusion equation tobe integrated at exponentially enhanced rates due to the nonuniformmesh spacing inherent in the log domain. The enhanced integrationrates, coupled with the intrinsic compression of the complex logtransformation, yields a speed increase of between two and threeorders of magnitude, providing a means of performing rapid imageenhancement using anisotropic diffusion.