[Retracted] Robust Zero Watermarking Algorithm for Medical Images Based on Zernike-DCT

Table 2

PSNR and NC values under different attacks.

Type of attacks	Parameter	PSNR	NC
Gaussian noise (%)	5	14.31	0.92
	10	11.86	0.92
	20	9.76	0.87
	30	8.77	0.68
JPEG compression (%)	20	33.81	1
	40	35.46	1
	60	36.42	1
	80	37.82	1
Median filter (5 times)	33	34.49	0.95
	55	29.95	0.91
	77	27.54	0.73
Rotation (°) (clockwise)	5	18.00	0.82
	10	15.60	0.82
	20	14.60	0.79
	30	14.40	0.70
	38	14.13	0.60
Scaling factor	0.4	—	0.68
	0.8	—	0.87
	1.2	—	1
	2	—	0.95
Movement (%) (left)	1	17.99	1
	5	14.48	0.91
	8	14.21	0.72
	10	13.82	0.63
Cropping (%) (Y direction)	3	—	0.91
	5	—	0.78
	10	—	0.74
	20	—	0.64