Question

I want to use mathematical morphology function in MATLAB to find the boundary of can.png image. The input image is:

I want to get a boundary such as :

I tried to use different combination and parameter using strel, imerode, imdilate , But the result is not good enough (far from the expectation)

One of my trial code is:

a = imread ('can.png');
b = im2bw(a);

SE = strel('rectangle', [10 50 ]) ;
i2 = imdilate(b,SE);

figure(1); imshow(i2);

p = ones(4);
c = b - imerode(b,p);

figure(2); imshow(c);

The output is:

Can any body help me, how to create the expected image (black background with thin boundary for the can, please? Thank you very much.

Answer 1

Binarize on its morphological gradient, then do a dilation with an elementary SE, fill holes and finally obtain its border (trivial given the current image). This doesn’t require any magical arbitrary threshold.