code: def get_scale_from_raw(raw, scaled):
          
          t0, t1 = scaled.min(), scaled.max()
          r0, r1 = float(raw.min()), float(raw.max())
  
          rmin = (t1*r0 - t0*r1) / (t1 - t0)
          rmax = (r1 - r0) / (t1 - t0) + rmin
          return (rmin, rmax)
docs: When given a raw image and the scaled version of the same image, it
          extracts the ``exposure`` parameters associated with those images.
          This is useful when
  
          Parameters
          ----------
          raw : array_like
              The image loaded fresh from a file
  
          scaled : array_like
              Image scaled using :func:`peri.initializers.normalize`
  
          Returns
          -------
          exposure : tuple of numbers
              Returns the exposure parameters (emin, emax) which get mapped to
              (0, 1) in the scaled image. Can be passed to
              :func:`~peri.util.RawImage.__init__`