Invisibility and readability of temporally and spatially intensity-modulated meta-image for information hiding on digital signage display system

This paper describes a display technique that can invisibly embed a meta-image in a color component of a displayed cover-image by using a temporally and spatially intensity modulated meta-image and extract it. We first examined invisibility in terms of colors for a temporally and spatially intensity modulated meta-image in a displayed cover-image. The results obtained from these experiments revealed that the invisibility with which the meta-image was embedded in the blue color component was much higher than that of the red and green components. We also proposed and evaluated a method of improving the readability of an invisibly embedded meta-image in a displayed cover-image captured with a video camera. The proposed method of calculating an estimated grayscale meta-image enabled us to obtain a value for the binarizing threshold from its histogram by using the correlation between color components in which the meta-image was either embedded or not embedded. The readability of the meta-image was drastically improved by using this method.