Previous robust image filters perform poorly on binary images, blur edges, round corners, and run slowly. I avoid artifacts on binary images by modelling them as continuous and interpolating values.
Information is combined directly between non-adjacent locations to prevent blurring.
Corners are sharpened by relabelling mis-classified pixels. Doc 84 Boundary Detection by Constrained Optimization - Geman, Geman et al. IJCV 6 - Meer, Mintz et al.