Recursive dither modulation based reversible watermarking scheme for medical images

In this paper, we propose a new and robust reversible watermarking scheme to address the security issue of medical images that are widely transmitted over internet. Reversible watermarking that embeds and extracts watermark using prediction and recursive dither modulation (RDM) algorithm is proposed. For each pixel, a predicted value is computed on a rhombus neighbourhood centered on the pixel and the corresponding prediction error is found out. If the prediction error is less than a threshold, then the pixel is modified using RDM algorithm to embed one bit of the scrambled watermark sequence. Superior experimental results are observed with the proposed scheme over the scheme proposed by Baiying Lei et al. in terms of peak signal to noise ratio (PSNR) and mean structural similarity index measure (MSSIM).