HDWT-based grayscale watermark for copyright protection

摘要

We propose a new algorithm based on Harr discrete wavelet transform for the grayscale watermark. Digital watermark is a very popular research for copyright protection of electronic documents and media. With quick developing of information technology, more and more information was been hidden in electronic media. We propose visual cryptographic approach to generate two random shares of a watermark: one is embedded into the cover-image, another one is kept as a secret key for the watermark extraction later. This procedure would be dealt with Harr discrete wavelet transform and be left primary features of two shares. This approach is specially designed and is not easily changed and removed. After several attacks, it can still extract cognoscible graphic.