Table 1.

Summary of all computed texture analysis categories with corresponding features.

Texture category	Texture feature
Histogram	Mean, variance, skewness, kurtosis
Grey-level co-occurrence matrix (GLCM) (computed for four directions [(a,0), (0,a), (a,a), (0,-a)] at five interpixel distances a = 1–5; 6 bits/pixel)	Angular second moment, contrast, correlation, entropy, sum entropy, sum of squares, sum average, sum variance, inverse different moment, difference entropy, difference variance
Run-length matrix (RLM) (computed for four angles [vertical, horizontal, 0°, and 135°]; 6 bits/pixel)	Run-length non-uniformity, grey-level non-uniformity, long run emphasis, short run emphasis, fraction of image in runs
Absolute gradient (4 bits/pixel)	Gradient mean, variance, skewness, kurtosis, and non-zeros
Autoregressive model	Teta 1–4, sigma
Wavelet transform (calculated for seven subsampling factors n = 1–7)	Energy of wavelet coefficients in low-frequency sub-bands, horizontal high-frequency sub-bands, vertical high-frequency sub-bands, diagonal high-frequency sub-bands