3D structuring element (sphere)

STREL3D creates a 3D sphere as a structuring element. Three-dimensional structuring elements are much better for morphological reconstruction and operations of 3D datasets. Otherwise the traditional MATLAB "strel" function will only operate on a slice-by-slice approach. This function uses the aribtrary neighborhood for "strel."

Usage:
se=STREL3D(sesize)

Arguments:
sesize - desired diameter size of a sphere (any positive integer)

Returns:
the structuring element as a strel class (can be used directly for imopen, imclose, imerode, etc)

Examples:
se=strel3d(1)
se=strel3d(2)
se=strel3d(5)

2014/09/26 - LX
2014/09/27 - simplification by Jan Simon