T Reduced Pixel Shifting and Improved Histogram Shifting Based Reversible Watermarking for Cartoon

The Hong’s modified histogram shifting method is best method of reversible watermarking. But Hong’s modified histogram method is not suitable for cartoon images. Our improved backward histogram shifting method overcome drawback of Hong’s method. Generally PSNR decreases when embedding capacity increases. But our improved backward histogram shifting method gives more embedding capacity and high PSNR. Hong’s method becomes unable to locate minimum point after 255 as generally histogram of cartoon images concentrates at 255 pixel value, which is called as maximum point. Our backward method finds minimum point before maximum point. Our improved backward histogram shifting method shifts required pixel values to left by ‘1’ numbers which is called minimum point. The embedding capacity for cartoon images is maximum because maximum numbers of pixels are available at 255, than any other images. The complexity of our improved histogram shifting backward method is same as that of Hong’s modified histogram shifting method as both scans image