Perceptual Image Hashing Based on Multitask Neural Network

Table 3

Statistics of hash distances under image content retention operations.

Operations	Min.	Max.	Mean	Std.
Speckle noise	1.8 × 10^−4	0.1751	0.0253	0.0377
Scaling	8.0 × 10^−5	0.0550	0.0046	0.0109
Median filtering	0	0.0091	0.0026	0.0025
Circle average filtering	0	0.2417	0.0512	0.0646
JPEG compression	1.3 × 10^−4	0.1138	0.0131	0.0253
Rotation and cropping	1.6 × 10^−3	3.2829	0.3724	0.7473
Gamma correction	5.9 × 10^−4	2.7986	0.2089	0.5312
Gaussian filtering	7.9 × 10^−4	0.1424	0.0268	0.0321