code: def mask_roi_digi(self):
          
          # http://stackoverflow.com/q/24205045/#24206440
          A = np.vstack([self.mask_1.mask_roi_sparse,self.mask_2.mask_roi_sparse]).T
          B = self.mask_roi_unique
  
          AA = np.ascontiguousarray(A)
          BB = np.ascontiguousarray(B)
           
          dt = np.dtype((np.void, AA.dtype.itemsize * AA.shape[1]))
          a = AA.view(dt).ravel()
          b = BB.view(dt).ravel()
           
          idx = np.argsort(b)
          indices = np.searchsorted(b[idx],a)
          return idx[indices]
docs: Get the index of the unique magnitude tuple for each pixel in the ROI.