Practical nonlinear filtering for removal of blotches from old film
Takahiro Saito, Takashi E. Komatsu, T. Ohuchi, T. Hoshi · 2003
The film material of old movies is often corrupted by blotches heavily. We present a practical method for removing blotches and restoring their missing data. To detect blotches, we employ a robust approach of local analysis of spatiotemporal anisotropic brightness continuity. Our approach selects the smoothest direction for each examined pixel, and puts out the incorruption probability that the examined pixel may not be corrupted by blotches. As the restoration filter, we employ a spatiotemporal nonlinear filter whose response is adaptively controlled according to a rule defined by the incorruption probability. The nonlinear filter is composed of the two different filters of the identity filter and the spatiotemporal anisotropic-smoothing filter, and will put out an intermediate value between the two filters' outputs. Furthermore, we introduce a protection method improving robustness against to errors of the anisotropic-continuity analysis.