Invisible and readable checkerboard as watermark with temporally brightness modulation

Abstract

This paper describes invisibility and readability in terms of the size of the basic unit of information that was attached to a displayed image by using our proposed method. The proposed method enables us to invisibly attach information to a displayed image on a flat panel display (FPD) and to extract the information from a captured video image of the displayed image. The information was attached to a single color component of the displayed image by using temporal and spatial brightness modulation. The information was arranged within a given rectangle area of the displayed image as a black and white checkerboard pattern. The checkerboard pattern was used because it is a typical example of a two-dimensional pattern with a high density. The checkerboard pattern consists of squares having the same side length. The side length of the square was changed to examine the invisibility and readability in terms of the size of the basic unit of information. First, we assessed invisibility to the human eye of the information attached to the displayed image on the FPD. The experimental results showed the range of the side length of the square that satisfied the invisibility of the information. We also examined readability of the attached information for a video camera. The experimental results showed a lower limit value of the side length of the square that satisfied the readability. The experimental results revealed the range of the side length of the squares that satisfied both the invisibility and readability of the information attached to the displayed image.