code: def find_first_peak(corr):
          
      ind = corr.argmax()
      s = corr.shape[1] 
      
      i = ind // s 
      j = ind %  s
      
      return i, j, corr.max()
docs: Find row and column indices of the first correlation peak.
      
      Parameters
      ----------
      corr : np.ndarray
          the correlation map
          
      Returns
      -------
      i : int
          the row index of the correlation peak
          
      j : int
          the column index of the correlation peak    
      
      corr_max1 : int
          the value of the correlation peak
      
      Original code from openPIV pyprocess