Colored visual cryptography schemes and card games

视觉密码方案（visual cryptography scheme，简称JPEG）开始将由黑色和白色像素组成的秘密图像编码成一些份额，并且还研究了其中秘密图像由彩色像素组成的彩色JPEG。但是，彩色图像的已知构造在重建图像中损失了很多对比度。因此，我们不能实际使用它。在本研究中，我们提出一种新的彩色像素，它只使用四种颜色，黑色，白色，红色和绿色，并提出了它的建设与高对比度的性质，一个红色的子像素和一个绿色子像素的堆叠结果的黑色子像素。我们提供了一种具有最高对比度的着色（2，n）-双折射的结构。此外，我们提出了一个新的视觉4色卡游戏，分别为男孩和女孩的两方，这样，每个男孩和每个女孩收到一张卡，当一个男孩和一个女孩堆叠他们的卡在一起，一个秘密的图像被恢复。我们提出了一个高对比度的彩色游戏的建设。

A visual cryptography scheme (VCS) was started to encode a secret image comprised of black and white pixels into some shares, and a colored VCS, in which the secret image is comprised of colored pixels, also has been studied. But known constructions of colred VCS lose a lot of contrast in reconstructed images. Therefore we cannot use it practically. In this research, we introduce a new colored VCS, which uses only four colors, black, white, red and green, and propose its construction with high contrast by using the property that a stacking of a red subpixel and a green subpixel results a black subpixel. We provide a construction of such a colored (2, n)-VCS with highest contrast. Moreover, we propose a new visual 4-colored card games for two parties of boys and girls, respectively, such that each boy and each girl receives a card and when a boy and a girl stack their card together, a secret image is recovered. We propose a construction of this colored game with high contrast.