Feature preserving coupled bidirectional flow for edge sharpening and image enhancement

In the past decade there has been a growing amount of research concerning partial differential equations in image enhancement. In this paper, a feature preserving coupled bidirectional flow is presented, where an inverse diffusion with a soft edge decision 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 (jaggies) along the tangent directions on the contrary. The two converse diffusion forces are split into a coupled form to stop the cancellation between each other. To preserve image features, the nonlinear diffusion coefficients are adjusted according to the local differential geometry of image. Experimental results demonstrate that the algorithm substantially improves the subjective quality of the enhanced images.