Fig. 6

Concept of screen column-shift method. a The four screens used to generate different patterns. The first screen is the 4×4 Bayer’s screen, and the other screens are generated by gradually shifting the column to the right. b The highlight encoding patterns (size 3) corresponding to a. c The shadow encoding patterns (size 3) corresponding to a. Each 4×4 halftone cell can be embedded with 2-b information by using b and c