Table 2.

Statistical features.

Feature Name	Formula	Feature Name	Formula
Mean intensity	$\frac{1}{N}{\displaystyle \sum _{i=1}^N}X\left(i\right)$	Skewness	$\frac{\frac{1}{N}{\displaystyle {\sum }_{i=1}^N}(X\left(i\right)-\stackrel{-}{X}{)}^3}{{\left(\sqrt{\frac{1}{N}{\displaystyle {\sum }_1^N}(X\left(i\right)-\stackrel{-}{X}{)}^2}\right)}^3}$
Standard deviation	${\left(\frac{1}{N-1}{\displaystyle \sum _{i=1}^N}(X\left(i\right)-\stackrel{-}{X}{)}^2\right)}^{1/2}$	Kurtosis	$\frac{\frac{1}{N}{\displaystyle {\sum }_{i=1}^N}(X\left(i\right)-\stackrel{-}{X}{)}^4}{{\left(\frac{1}{N}{\displaystyle {\sum }_1^N}(X\left(i\right)-\stackrel{-}{X}{)}^2\right)}^2}$
Entropy	${\displaystyle \sum _{i=1}^{N_1}}P\left(i\right).{\mathit{log}}_{2}P\left(i\right)$