Table 1.

Two-order statistical parameters.

Method	Equation	Description
Angular second moment (ASM)	$ASM={\displaystyle \sum _i^N{\displaystyle \sum _j^{N}P(i,j{)}^2}}$
Contrast (CON)	$CON={\displaystyle \sum _i^N{\displaystyle \sum _j^N{(i-j)}^{2}P(i,j)}}$
Correlation (COR)	$COR=\frac{{\displaystyle \sum _i^N{\displaystyle \sum _j^N(i-\overline{x})(j-\overline{y})P(i,j)}}}{{\sigma }_x{\sigma }_y}$	$\begin{array}{c}\overline{x}={\displaystyle \sum _i^{N}i{\displaystyle \sum _j^{N}P(i,j)}} \overline{y}={\displaystyle \sum _j^{N}j{\displaystyle \sum _i^{N}P(i,j)}}\\ {{\sigma }_x}^2={\displaystyle \sum _i^N{(i-\overline{x})}^2{\displaystyle \sum _j^{N}P(i,j)}}\\ {{\sigma }_y}^2={\displaystyle \sum _j^N{(j-\overline{y})}^2}{\displaystyle \sum _i^{N}P(i,j)}\end{array}$
Entropy (ENT)	$ENT=-{\displaystyle \sum _i^N{\displaystyle \sum _j^{N}P(i,j)\lg P(i,j)}}$