A separable reversible data hiding scheme for encrypted images based on Tromino scrambling and adaptive pixel value ordering

摘要

To further improve capacity and reduce distortion, a novel separable reversible data hiding (RDH) scheme for encrypted images based on Tromino scrambling and adaptive pixel value ordering (PVO) is proposed. An image is first partitioned into non-overlapped blocks with three pixels in L shape, and then Tromino scrambling and stream encryption are performed to the blocks in sequence. In the embedding phase, an adaptive pixel value ordering (PVO) scheme is utilized. The differences between the smallest pixel value and the rest two pixel values are calculated, and the pairwise prediction errors corresponding to each block is accumulated to form a two-dimensional prediction error histogram. Subsequently, an adaptive 2D histogram mapping is established for reversible data hiding. Experimental results and analysis show that it is separable and can completely recover the original image. Furthermore, compared with other PVO, the adaptive PVO makes better use of the features of the images after Tromino encryption, it can achieve larger capacity and better visual quality of the decrypted images compared with the existing methods.