Preserving robustness and removability for digital watermarks using subsampling and difference correlation

Watermarking techniques are applied to digital media to protect their integrity and copyright. The embedding of a watermark, however, often distorts the quality of the protected image. This may be intolerable since the protected media is for preserving artistic and valuable images. Hence, engineers have proposed removable solutions permitting authorized users to restore watermarked images to unmarked images with satisfactory quality. Unfortunately, these mechanisms cannot resist signal processing attacks to protect the ownership. In this article, we propose a novel watermarking mechanism by utilizing pair-difference correlations upon subsampling and the technique of JND. This new approach can guarantee the robust essentials of watermarking schemes. Experimental results reveal that the new method outperforms others in terms of restored image quality. More specifically, this novel approach can resist various attacks to which related works are vulnerable.