Color Zero-Watermarking Algorithm for Medical Images Based on BEMD-Schur Decomposition and Color Visual Cryptography

Table 2

NC values under additive Gaussian, salt and pepper, and speckle noise attacks.

Attack type	Attack intensity	Fundus1	Fundus2	Fundus3	Fundus4	Cerebral1	Cerebral2	Cerebral3	Cerebral4
Gaussian noise	0.01	0.9925	0.9916	0.9928	0.9888	0.9911	0.9912	0.9926	0.9909
	0.03	0.9842	0.9771	0.9789	0.9716	0.9780	0.9800	0.9834	0.9791
	0.05	0.9768	0.9681	0.9650	0.9517	0.9650	0.9661	0.9723	0.9688
Salt and pepper noise	0.01	0.9975	0.9951	0.9971	0.9927	0.9955	0.9957	0.9968	0.9954
	0.03	0.9940	0.9903	0.9909	0.9841	0.9912	0.9913	0.9946	0.9907
	0.05	0.9903	0.9843	0.9856	0.9777	0.9868	0.9885	0.9907	0.9884
Speckle noise	0.01	0.9981	0.9974	0.9987	0.9987	0.9974	0.9983	0.9988	0.9989
	0.03	0.9966	0.9953	0.9990	0.9978	0.9972	0.9969	0.9970	0.9971
	0.05	0.9961	0.9941	0.9979	0.9961	0.9956	0.9962	0.9964	0.9958