Society of Photo-optical Instrumentation Engineers (SPIE)
This paper describes a visual cryptography method for the elimination of pixel expansion and the improvement of contrast. The proposed method uses the probability concept to construct a multiobjective linear programming model for general access structures. Then, the solution space of the model is explored by goal programming. The advantages of the proposed method are fourfold. First, it can avoid expanding the shadow images. Second, it can reach better contrast. Third, it can deal with general access structures and get the desired contrast levels. Fourth, it can be easily extended to deal with the problems of multiple secret images. Experiments on several access structures show that the proposed method is effective against pixel expansion and is capable of contrast improvement.