Figure 4

Sample of scrambled images. a DC coefficients are scrambled, \(SSIM=0.3882.\) b Blocks of AC coefficient are scrambled, \(SSIM = 0.1464.\) c Blocks of \(8\times 8\) coefficients are scrambled, \(SSIM = 0.1519.\) d DC and AC coefficients are separately scrambled, \(SSIM = 0.1435.\)