MATLAB: How should I create ring(circular) shaped structuring element

Question

I am working on a project related to malaria detection and severity from infected red blood cells for that i need ring shaped structural element to do morphological operation.

Answer 1

You can specify any arbitrary neighbourhood matrix to strel. You could generate that ring matrix by subtracting two disk structural elements of different radii, e.g.:

outerradius = 6;
innerradius = 4;
outerdisk = strel('disk', outerradius);
innerdisk = strel('disk', innerradius);
ringmatrix = outerdisk.Neighborhood - padarray(innerdisk.Neighborhood, repmat(outerradius - innerradius, 1, 2));
ringelement = strel(ringmatrix);