GLCM Variance (GLCM Standard Deviation)
Variance equation
Standard deviation
equation
Calculation details:
GLCM Variance in texture measures performs the same task as does the common descriptive statistic called variance. It relies on the mean, and the dispersion around the mean, of cell values within the GLCM. However, GLCM variance uses the GLCM, therefore it deals specifically with thedispersion around the mean of combinations of reference and neighbour pixels, so it is not the same as the simple variance of grey levels in the original image.
Variance calculated using i or j gives the same result, since the GLCM is symmetrical.
There is no particular advantage to using Standard Deviation over Variance, other than a different range of values.
Properties of Variance
Variance is a measure of the dispersion of the values around the mean. It is similar to entropy. It answers the question "What is the dispersion of the difference between the reference and the neighbour pixels in this window?"
Exercise: Calculate the Variance texture for
both the horizontal and vertical GLCM of the test image.