A Strong Robust Zero-Watermarking Scheme Based on Shearlets’ High Ability for Capturing Directional Features

Table 4

The values of distorted host images and values of extracted watermarks after median filtering.

Host image	Median filter	Median filter	Median filter
	SSIM/NC	SSIM/NC	SSIM/NC
Boat	0.93/0.9823	0.83/0.9862	0.75/0.9849
Goldhill	0.89/0.9744	0.77/0.9711	0.69/0.9697
Baboon	0.73/0.9596	0.51/0.9515	0.42/0.9576
Barbara	0.84/0.9836	0.67/0.9830	0.65/0.9643
Peppers	0.89/0.9993	0.85/0.9987	0.83/0.9987
Man	0.90/0.9796	0.80/0.9750	0.73/0.9710