code: def snr(vref, vcmp):
      
  
      dv = np.var(vref)
      with np.errstate(divide='ignore'):
          rt = dv / mse(vref, vcmp)
      return 10.0 * np.log10(rt)
docs: Compute Signal to Noise Ratio (SNR) of two images.
  
      Parameters
      ----------
      vref : array_like
        Reference image
      vcmp : array_like
        Comparison image
  
      Returns
      -------
      x : float
        SNR of `vcmp` with respect to `vref`