MATLAB: How to delete an object without a dot on it

Question

Hi, I am trying to extract the mobile phone, with a dot on it, out of the image. I have detected the edge of the phone. But beside the phone there is a cap without a dot, which I don't want. How should I delete the image of the cap and extract only the phone? I have already got the coordinate of the dot center.

Answer 1

You can use bwlabel to label the binary image,

L = bwlabel(I);

then get the label of the phone using the coordinates of the red dot, create an empty image the size of the original one, and then set only the pixels in the new image that match the label of the phone to 1:

Inew = zeros(size(I));  
Inew(L==L(y_red, x_red)) = 1;