Computes the local standard deviation in a neighbourhood around each pixel in an image.
The standard deviation of the pixels of a neighbourhood is computed as
S = sqrt ((sum (x - mu).^2)/(N-1))
where mu is the mean value of the pixels in the neighbourhood, N is the number of pixels in the neighbourhood. So, an unbiased estimator is used.
The neighbourhood is defined by the domain binary mask. Elements of the mask with a non-zero value are considered part of the neighbourhood. By default a 3 by 3 matrix containing only non-zero values is used.
At the border of the image, extrapolation is used. By default symmetric
extrapolation is used, but any method supported by the padarray function
can be used. Since extrapolation is used, one can expect a lower deviation near
the image border.
See also: std2, paddarray, entropyfilt.
Package: image