Reversible Watermarking Based on Improved Patchwork Algorithm and Symmetric Modulo Operation

Abstract

Modulo operations are often used in reversible watermarking scheme.However, the modulo operations would cause an annoying visual artifact similar to the “salt-and-pepper” noise when pixel value close to the maximally allowed value are flipped to zero and vice versa. To prevent the “salt-and-pepper” noise, the paper presents reversible watermarking scheme using improved patchwork and an improved modulo operation. The improved modulo operation called symmetric modulo operation effectively avoids “salt-and-pepper” noise by the reasonably reducing the flipping distance. Experimental results show that correctly watermark bits can be retrieved by the patchwork algorithm without the original image and that the original image can be restored perfectly while the perceptual degradation of the watermarked signal remained acceptable.