Hierarchical embedment of supplementary information into character patterns by changing color

With development of cyber physical systems, information hiding technology that can go through the real environment has been expected, while some methods for embedding supplementary information into character patterns for improving recognition accuracy have been studied. If we change the design of character patterns drastically, it will become unnatural and readability will be lost. Supplementary information should be embedded as a natural design for humans, and it should be accurately extracted by using a camera. In this paper, utilizing the fact that human eyes are less sensitive to the change in color than in the luminance, we propose a method for improving recognition accuracy by embedding supplementary information hierarchically into character patterns by changing color of the region to some extent where it will not be visible for human.