samer@4: function B = rot45(A)
samer@4: % rot45 - rotate square array by 45 degrees
samer@4: %
samer@4: % rot45 :: [[N,N]] -> [[N,N]].
samer@4: %
samer@4: % Array is SUBSAMPLED, so, you should pre-filter to avoid aliasing.
samer@4: % Result is padded with zeros in the corners.
samer@4: 
samer@4: n = length(A);
samer@4: 
samer@4: B = diag(A,0)';
samer@4: pad = [0];
samer@4: 
samer@4: for k=2:2:n-1
samer@4: 	B = [ pad diag(A,k)' pad; B; pad diag(A,-k)' pad];
samer@4: 	pad = [pad 0];
samer@4: end