Connected components for periodic image

I'm trying to test for the connectivity of pixels in a square 2D binary image, but the catch is the image repeats itself periodically.

I'm wondering if I can do this using something like bwconncomp, but I'm having trouble implementing the periodic boundary condition.

For example, say I enter

B = [1 0 0 0;
     0 0 0 0;
     0 0 0 0;
     0 0 0 1];

CC = bwconncomp(B,8)   % I'm considering 8 connectivity

I get

CC = 

      Connectivity: 8
         ImageSize: [4 4]
        NumObjects: 2
      PixelIdxList: {[1]  [16]}

With the new code, I would get 1 object with PixelIdxList returning {[1; 16]}

Your help would be greatly appreciated...

Answer 1

[Image Analyst]

I think you'll have to "manually" relabel the blobs on the other side based on their location. Scan the border and if there's a blob there, see if there is a blob on the other side that would be touching it. If there is, reassign it's label to the blob that you're working on.

[Geoff Stanley]

I had the same problem. I've written a function that does this task, called CC2periodic, available at https://uk.mathworks.com/matlabcentral/fileexchange/66079-cc2periodic