code: def precompute_sharp_round(nxk, nyk, xc, yc):
      
  
      # Create arrays for the two- and four-fold symmetry computations:
      s4m = np.ones((nyk,nxk),dtype=np.int16)
      s4m[yc, xc] = 0
  
      s2m = np.ones((nyk,nxk),dtype=np.int16)
      s2m[yc, xc] = 0
      s2m[yc:nyk, 0:xc]     = -1;
      s2m[0:yc+1, xc+1:nxk] = -1;
  
      return s2m, s4m
docs: Pre-computes mask arrays to be used by the 'sharp_round' function
      for roundness computations based on two- and four-fold symmetries.