A Shock-diffusion Equation with Local Coupling Term for Image Sharpening
Wenqia Wang · Journal of Optoelectronics·laser · 2007
A shock-diffusion equation with local coupling term is presented,where an inverse diffusion(shock)is performed to sharpen edges along the normal directions to the isophote lines(edges),while a normal diffusion is done to remove noise and artifacts(“jag-gies”)along the tangent directions on the contrary.To overcome the false result with piecewise constant regions produced by the binary zero-crossing decision process,a hyperbolic tangent function is used to substitute the symbol function,governing softly the varieties of gray levels of pixels beside the zero-crossing of edges.A local coupling term is added to the shock-diffusion equation,to further control it to approach a steady process avoiding explosion and overshoots.Experimental results demonstrate that the algorithm improves substantially the visual quality of image.