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

Table 6

NC values under geometric scaling attacks.

Attack type	Attack intensity	Fundus1	Fundus2	Fundus3	Fundus4	Cerebral1	Cerebral2	Cerebral3	Cerebral4
Scaling	0.5	0.9990	0.9995	0.9995	0.9994	0.9918	0.9967	0.9935	0.9929
	0.75	0.9987	0.9997	0.9992	0.9995	0.9941	0.9972	0.9954	0.9955
	1.5	0.9992	0.9998	0.9998	0.9999	0.9976	0.9988	0.9981	0.9979