Vectorized Color Modulation for Covert Camera-Screen Communication

We propose a vectorized color modulation (VCM) method for a covert camera-screen communication (CSC) system under the human visual constraint. Instead of using light intensity of each image pixel block for data modulation in the existing work, we explore the color mixing characteristics of different colors while maintaining the chromaticity perception quality. Thus a color vector in the chromatic diagram can carry information in its angle, revealing a new signal dimension and mitigating the flickering issue. The best color vector pair is searched and selected for data modulation to yield the lowest bit error rate (BER). Experimental test based on representative images from an open database shows that the proposed method yields much better communication performance than the existing intensity modulation method.