Table 2.

List of local image features previously proposed in [19,32,61]

No.	Feature
1	Region conspicuity
2	Region size
3	Region contrast
4	Average local noise (pixel value fluctuation)
5	Standard deviation of local noise
6	Skewness of local noise
7	Mean radial length / region size
8	Standard deviation of radial lengths
9	Skewness of radial lengths
10	Ratio between the maximum and minimal radial length
11	Shape factor ratio (perimeter of boundary2 / region size)
12	Region circularity
13	Standard deviation of pixel values inside growth region
14	Skewness of pixel values inside growth region
15	Kurtosis of pixel values inside growth region
16	Average value of gradient of boundary contour pixels
17	Standard deviation of gradient of boundary contour pixels
18	Skewness of gradient of boundary contour pixels
19	Standard deviation of pixel values in the surrounding background
20	Skewness of pixel values in the surrounding background
21	Kurtosis of pixel values in the surrounding background
22	Average noise of pixel values in the surrounding background
23	Standard deviation of pixel value noise in the surrounding background
24	Skewness of pixel value noise in the surrounding background
25	Ratio of number of “minimum” pixels inside growth region
26	Average pixel value depth of “minimum” pixels inside growth region
27	Center position shift (distance between gravity center and local minimum) / region size