Improved histogram bin shifting based reversible watermarking

Reversible w atermarking constitutes a class of fragile digital watermarking techniques that find application in authentication of medical and military imagery. Reversible watermarking techniques ensure that after watermark extraction, the original cover image can be recovered from the watermarked image pixel-by-pixel. In this paper, we propose a novel reversible watermarking technique as an improved modification of the existing histogram bin shifting technique. We develop an optimal selection scheme for the “embedding point” (grayscale value of the pixels hosting the watermark), and take advantage of multiple zero frequency pixel values (if available) in the given image to embed the watermark. Experimental results for a set of images show that the adoption of these techniques improves the peak signal-to-noise ratio (PSNR) of the watermarked image compared to previously proposed histogram bin shifting techniques.