Efficient PVO-based reversible data hiding using multistage blocking and prediction accuracy matrix

In recent years, pixel value ordering based reversible data hiding has become a hot research topic for its high-fidelity. In this approach, only the maximum and minimum of pixel block are predicted and modified to embed data and the preservation of pixel values order guarantees the reversibility. So far, the optimal block size can only be exhaustively searched until Wang et al. propose the dynamic blocking strategy which enables the combination of two various-sized blocks. By further dividing flat block into four sub-blocks to retain larger embedding capacity, dynamic blocking can employ less high complexity blocks for a given embedding capacity. However, the lack of host image dependent automatic block classification mechanism still exposes the fact that their work is far from efficient and comprehensive. In this paper, to address this drawback and to better exploit image redundancy, a really efficient and more comprehensive blocking strategy namely multistage blocking is proposed. High efficiency lies in prediction accuracy matrix based thresholds determination, which enables infinitely extended multistage blocking in theory. The superiority of the proposed scheme is also experimentally verified.