A novel reversible image data hiding scheme based on pixel value ordering and dynamic pixel block partition

Recently, various efficient reversible data-hiding schemes based on pixel value ordering have been proposed for embedding messages into high-fidelity images. In these schemes, after dividing the cover image into equal-sized blocks, the pixels within a given block are ordered according to their values, and data embedding is achieved by modifying the maximum and minimum values of each block. For a given embedding capacity, the optimal block size is exhaustively searched so that the embedding distortion is minimized. These pixel value ordering-based schemes perform fairly well, especially for low embedding capacity. However, to obtain a larger embedding capacity, a smaller block size should be used, which usually leads to a dramatic quality degradation of the marked image. In this paper, to address this drawback and to enhance the performance of pixel value ordering-based embedding further, a novel reversible data hiding method is proposed. Instead of using equal-sized blocks, a dynamic blocking strategy is used to divide the cover image adaptively into various-sized blocks. Specifically, flat image areas are preferentially divided into smaller blocks to retain high embedding capacity, whereas rough areas are divided into larger blocks to avoid decreasing peak signal-to-noise ratio. As a result, the proposed scheme can provide a larger embedding capacity than current pixel value ordering-based schemes while keeping distortion low. The superiority of the proposed method is also experimentally verified.