Local sparse representation optimized to edge orientation for inverse halftoning

A method is proposed for fully restoring local image structures of an unknown continuous-tone patch from an input halftoned patch with homogenously distributed dot patterns, based on locally learned dictionary pairs via feature clustering. Experimental results show that the use of the paired dictionary selected by the local edge orientation enables the restored continuous-tone images to include well-expressed fine details and outlines, especially in the areas of textures, lines, and regular patterns.