Improved dual-image reversible data hiding method using the selection strategy of shiftable pixels' coordinates with minimum distortion

Compared to conventional reversible data hiding (RDH) methods, the dual-image RDH technique is an effective way to achieve greater embedding rate and better quality of the stego images. Motivated by the center folding-based, dual-image RDH method proposed by Lu et al. (SIGNAL PROCESSING, 115 (2015) 195-213), we propose an improved dual-image RDH method by using the selection strategy of shiftable pixels' coordinates with minimum distortion. Although the stego dual-pixel in the center folding-based method is shifted with minimum distortion, there is another shiftable pixel-coordinate that can be used without creating any extra distortion. Based on this observation, the embedding rate can be improved without any deterioration of visual quality by embedding an extra message bit into each newfound alternative pixel-coordinate. In addition, the range of parameter k, which controls the embedding rate, in our method is extended to greater than or equal to 1, therefore, a higher visual quality can be achieved when k is set at 1. The experimental results showed that the embedding rate of our method is greater than that of the center folding-based method for the same stego image quality, and our method outperforms other methods, whether in term of average PSNR or embedding rate.