MATLAB: 3×3 8-connected structuring element

Question

How exactly does a 8-connected 3×3 structuring element looks like in a matrix form?

Answer 1

If you use a integer or double class, it's

1  1  1
1  1  1
1  1  1

which is the same as

se = ones(3); % <= double, or:
se = ones(3, 'uint8'); % <= uint8

or for a logical / boolean class:

true true true
true true true
true true true

which is the same as

se = true(3);

You can also use the strel function

se = strel('disk', 5);

where se is a special class of type 'strel'.

I usually use the logical form when I make up a structuring element manually.