TABLE 1.

Gray-Level Histogram Texture Features

Gray-level histogram features	Qualitative description	Mathematical description
Mean	Mean gray-level value	$\sum k\frac{k*g(k)}{\sum kg(k)}$
Min	Min gray-level value	Min(k)
Max	Max gray-level value	Max(k)
5th Percentile	Histogram bin that 5% of gray-level values are less than or equal to	k: 5% of values ≤ k
Mean 5th	Mean value of gray-level values that 5% of gray-level values are less than or equal to	$\frac{{\sum }_{k}k*g\left(k\right)}{\sum kg\left(k\right)}\text{for}k\le \text{fifth}\text{percentile}$
95th Percentile	Histogram bin that 95% of gray-level values are greater than or equal to	k: 95% of values ≥ k
Mean 95th	Mean value of gray-level values that 95% of gray-level values are greater than or equal to	$\frac{{\sum }_{k}k*g\left(k\right)}{\sum kg\left(k\right)}\text{for }k\ge \text{ ninety-fifth percentile}$
Sum	Sum of gray-level values	${\sum }_{k}k*g\left(k\right)$
Sigma	Measure of variation of gray-level values around the mean	$\sqrt{{\sum }_k{(k-\mu )}^2*g(k)}$
Entropy	Measure of histogram nonuniformity	$-{\sum }_{k}g(k)*\text{log}(g(k))$
Kurtosis	Measure of histogram flatness	${\sigma }^{-4}{\sum }_k{(k-\mu )}^4*g(k)-3$
Skewness	Measure of histogram symmetry	${\sigma }^{-3}{\sum }_k{(k-\mu )}^3*g(k)$