MATLAB: Counting the neighbors in matrix

histogramMATLABmatrixneighbor pixels

Hi everyone,
I have matrix R in which each element is integer of range [0 7]. I want to calculate the count of neighbor, let say for pixel value 0 how many times it has the neighbor 1, 2, …, 7. every pixel has eight neighbors, for example
[n1 n2 n3
 n4 x  n5
 n6 n7 n8]
where pixel x have eight neighbors. As a resultant I think we will have an other matrix of 8 x 8, or we can say 8 histograms as we have eight possible values in given matrix R.
I hope I have explained what I want 🙁

Best Answer

If you don't have the image processing toolbox, or if you want your code to be useful to those who don't, this is just as fast. Note that the example only looks for the neighbors of the number 7. You can put this into a loop as needed. I assume your matrix is named x.
H = single(x==7);
H = logical(conv2(H,ones(3),'same'))~=H;
H = x(H(:));
Y = unique(H);   
H = histc(H,Y); 
H = [Y H];
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