code: def normalize(im, invert=False, scale=None, dtype=np.float64):
      
      if dtype not in {np.float16, np.float32, np.float64}:
          raise ValueError('dtype must be numpy.float16, float32, or float64.')
      out = im.astype('float').copy()
  
      scale = scale or (0.0, 255.0)
      l, u = (float(i) for i in scale)
      out = (out - l) / (u - l)
      if invert:
          out = -out + (out.max() + out.min())
      return out.astype(dtype)
docs: Normalize a field to a (min, max) exposure range, default is (0, 255).
      (min, max) exposure values. Invert the image if requested.