基于误差扩散算法的（2，2）可视密码方案

为解决传统可视密码存在像素膨胀及分存图像无意义等问题，研究并实现了将黑白反色的密图嵌入到两个灰度图像的方法。通过采用对灰度图像进行预处理增加分存图像叠加后，黑色像素恢复的概率以及在误差扩散的过程中同时嵌入密图信息、适当降低白色像素恢复概率以及恢复黑色像素时随机选择修改其中一个分存图像的方法，有效地提高了分存图像的质量。方案符合可视密码解密简单的特性且分存图像有意义，没有引入任何像素膨胀。

(2,2)Visual Cryptographic Scheme Based on Error Diffusion Algorithm

Conventional VCS（visual cryptographic scheme） suffers from complicated construction method, pixel expansion and meaningless share images. To solve these problems, a （2, 2） VCS based on error diffusion algorithm with a black-white secret image embedded into the two gray carrier images is proposed and implemented. The preprocess of gray images is introduced to improve the probability for recovery of black pixels. The embedment of secret image is done in the process of error diffusing. For the purpose of safety, the probability for recovery of white pixels could be decreased. Experiment results indicate that the proposed scheme could realize the easy decoding of visual cryptography, the construction method is simple, and the achieved shares are meaningful and of high quality, while without any introduction of pixel expansion.