. 2023 Apr 7;12(8):2762. doi: 10.3390/jcm12082762

Table A2.

Formulae to calculate gray level co-occurrence matrix from the gray-scale image.

Feature Name	Formulae
Contrast	$\sum_{i = 0}^{G - 1} \sum_{j = 0}^{G - 1} {(i - j)}^{2} p (i, j)$	(A6)
Correlation	$\sum_{i = 0}^{G - 1} \sum_{j = 0}^{G - 1} \frac{i j p (i, j) - µ_{i} µ_{j}}{δ_{i} δ_{j}}$ where µ_i is average and δ_i is standard deviation for p_i	(A7)
Homogeneity	$\sum_{i = 0}^{G - 1} \sum_{j = 0}^{G - 1} \frac{p (i, j)}{{1 + (i - j)}^{2}}$	(A8)
Entropy	$- \sum_{i = 0}^{G - 1} \sum_{j = 0}^{G - 1} p (i, j) {l o g}_{2} (p (i, j))$	(A9)
Angular second moment	$\sum_{i = 0}^{G - 1} \sum_{j = 0}^{G - 1} p^{2} (i, j)$	(A10)
Sum average	$\sum_{m = 1}^{G} m p_{s u m} (m)$	(A11)
Sum variance	$\sum_{m = 1}^{G} {(m - s u m - a v g)}^{2} p_{s u m} (m)$	(A12)
Difference variance	$\sum_{m = 1}^{G} {(i - µ_{d i f})}^{2} p_{d i f} (m)$	(A13)
Difference entropy	$- \sum_{m = 1}^{G} p_{d i f} (m) \log (p_{s u m} (m))$	(A14)
Sum entropy	$- \sum_{m = 1}^{G} p_{s u m} (m) \log (p_{s u m} (m))$	(A15)
Sum of squares	$\sum_{i = 0}^{G - 1} \sum_{j = 0}^{G - 1} {(i - µ)}^{2} p (i, j)$	(A16)