A VSS Scheme of Image Size Invariant for Vertical Edge Enhancement

We proposed a visual cryptography scheme based on Tu and Houpsilas visual cryptographic method to enhance the contrast and visibility for gray-level images. With more detailed distribution of codebooks, we could get good identification for those vertical edges of secret image. Especially, the smaller the image size, the better the contrast. Besides strengthening the reorganization, ours proposed scheme also has the advantage of no-expansion of decoded image.