Zero-Watermarking Algorithm for Medical Image Based on VGG19 Deep Convolution Neural Network

Table 2

The images under ripple distortion attack.

	Medical image A	Medical image B	Medical image C	Medical image D	Medical image E
The smallest NC value	0.74818	0.68929	0.59668	0.81021	0.68872
The restored watermarking image
Medical image to be tested