Novel Non-expanded Visual Cryptography Scheme with Block Encoding

Yi-Jing Huang ； Chih-Chiang Lee ； Hsien-Chu Wu ； Jun-Dong Chang ； Chwei-Shyong Tsai ； Ya-Ting Tsao

《電腦學刊》 22卷2期 (2011/07) Pp. 61-71

並列摘要

In the traditional visual cryptography, secret pixels are expanded to cause the size of the recovered image is larger than the original one. Although many researches successfully solve expansion problem, the quality of the recovered image is not better. In order to improve quality of reconstruction, this paper proposes a novel non- expansion scheme. The principle of the proposed scheme is to divide the secret image into a number of blocks in the first place and then each block generates a number of combinations of share blocks by using same color pixels. After generating combinations of share blocks, two pixels with a corresponding position are executed by the ”OR” operation when stacking two share images. In spite of solving the expansion problem and increasing the clearly visible of the recovered image, the result of the proposed scheme tends towards dark. In order to increase contrast of the recovered image, the second scheme is proposed by modifying original secret blocks before dividing the secret image into blocks, and then the further processes are in common as the first scheme. From the experimental results, the image quality of the second scheme is clearer than the first scheme.

並列關鍵字

Visual cryptography ； non expanded ； block encoding