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

Table 4

NC values under JPEG compression attacks.

Attack type	Attack intensity (%)	Fundus1	Fundus2	Fundus3	Fundus4	Cerebral1	Cerebral2	Cerebral3	Cerebral4
JPEG compression	10	0.9945	0.9897	0.9949	0.9840	0.9843	0.9906	0.9926	0.9860
	30	0.9955	0.9898	0.9952	0.9913	0.9903	0.9954	0.9958	0.9954
	50	0.9983	0.9975	0.9973	0.9963	0.9936	0.9971	0.9970	0.9946
	70	0.9985	0.9978	0.9978	0.9979	0.9948	0.9969	0.9977	0.9944