code: def normalizedGraylevelVariance(img):
      ''''GLVN' algorithm (Santos97)'''
      mean, stdev = cv2.meanStdDev(img)
      s = stdev[0]**2 / mean[0]
      return s[0f normalizedGraylevelVariance(img):
      ''''GLVN' algorithm (Santos97)'''
      mean, stdev = cv2.meanStdDev(img)
      s = stdev[0]**2 / mean[0]
      return s[0]
docs: GLVN' algorithm (Santos97)