std

\(f_{1}=\sqrt {\sum \limits _{i}(imean)^{2}H\,(i)}\)

The standard deviation of

 
intensity from all the pixels

 
in a region.

Smoothness

\(f_{2}=1\frac {1}{(1+{f_{1}^{2}})}\)

The relative smoothness of the

 
intensity in a region. It is 0 for a

 
region of constant intensity and

 
1 for a region with large excursion

 
in the values of its intensity levels.

Skewness

\(f_{3}=\sum \limits _{i}(imean)^{3}H\,(i)\)

The order moment about the

 
mean. The departure from

 
symmetry about the mean

 
intensity. It is 0 for symmetric

 
histograms, positive for

 
histograms skewed to the right

 
and negative for histograms

 
skewed to the left.

Uniformity

\(f_{4}=\sum \limits _{i}H^{2}\,(i)\)

The sum of squared elements in

 
Histogram. It reaches maximum

 
when all intensity levels are equal

 
and decreases from there.

Entropy

\(f_{5}=\sum \limits _{i}H(i)\log _{2}{H\,(i)}\)

The statistical measure of

 
randomness.
