How many ways to define shape and size of structuring element depend on images in Watershed segmentation?

% Here a sample matlab code for MC-Watershed Segmentation
% Please ! help me, I would like to obtain structuring element arbitrarily, depending on images

rgb = imread(name);
I = rgb2gray(rgb);
hy = fspecial('sobel');
hx = hy';
Iy = imfilter(double(I), hy, 'replicate');
Ix = imfilter(double(I), hx, 'replicate');
gradmag = sqrt(Ix.^2 + Iy.^2);
%this is fixed structuring element in tool ,So I would like to change that
se = strel('disk',20);
Io = imopen(I, se);   
Ie = imerode(I, se);  
Iobr = imreconstruct(Ie, I);
Ioc = imclose(Io, se); %closing
Iobrd = imdilate(Iobr, se);
Iobrcbr = imreconstruct(imcomplement(Iobrd), imcomplement(Iobr));
Iobrcbr = imcomplement(Iobrcbr);
fgm = imregionalmax(Iobrcbr);
I2 = I;  
I2(fgm) = 255;
se2 = strel(ones(5,5));
fgm2 = imclose(fgm, se2);
fgm3 = imerode(fgm2, se2);
fgm4 = bwareaopen(fgm3,10);  %shink them a bit e.g 20
I3 = I;
I3(fgm4) = 255;
.
.
...
.....
%Please ,suggest me

Answer 1

[Walter Roberson]

strel() can take 'arbitrary' matrices for the neighborhood. You are working on 2D matrices, so you want your strel matrix to be 2D. All arbitrary rectangular matrix sizes between 1 x 1 to size(I,1) to size(I,2) can be used. For each matrix size, each position can be either 0 or 1, so each matrix can be filled in 2^numel(matrix) ways.

2^(1 * 1) + 2^(1 * 2) + 2^(2 * 1) + 2^(1 * 3) + 2^(3 * 1) + 2^(1 * 4) + 2^(4 * 1) + 2^(2 * 2) + ....

So basically unless your original image is no more than roughly 6 x 6, automatically generating and applying all the possible structuring elements is going to take the computer rather some time. In view of the alternatives, are you sure this is wise?

[kyawt kyawt]

Thanks for your answer.