Selective sharpness enhancement of corrupted old film sequences by coupled nonlinear reaction-diffusion time-evolution
Takahiro Saito, Kentarou Yashiro, Jun Satsumabayashi, Takashi Komatsu · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2002
In old movie film, most of sharp brightness transitions have been blurred, and film materials are often corrupted by several distortions such as blotches. To restore original edge sharpness without augmenting visibility of such distortions, first we characterize such distortion areas, repair them and then sharpen only blurred edges selectively. This paper presents a locally-adaptive sharpening method based on the coupled nonlinear reaction-diffusion time-evolution equipped with a second-order nonlinear smoothing term, a reaction term and an overshooting term. The overshooting term adds an overshoot only to the blurred edges. The coupled nonlinear reaction-diffusion method utilizes information about local image contents and the characterized film distortions, to control the degree of the second-order smoothing and the magnitude of the overshoot to be added. Our method sharpens blurred edges selectively much better than our previously presented adaptive peaking method. Our method, of course, is applicable to sharpness enhancement of general blurred images.