A new M4 matrix based scheme of Visual Cryptography for grey level images

By analysing the character of Visual Cryptography for grey level images and dither technology in image processing, a new M4 matrix based scheme of Visual cryptography for grey level images is proposed. Schemes of visual cryptography for grey level images are considered using dither technology in image processing, and a new method are provided: M4 matrix based scheme of Visual Cryptography for grey level images. The advantage using M4 matrix based scheme of Visual cryptography for grey level images is that the computational complexity decays, time complexity is reduced, and the basic matrices of Visual cryptography for binary images can be utilized directly, the pixel expansion is controlled, so the size of the share transparencies is smaller then before.