code: def from_lt(rsize, ltm, ltv):
      
      dbinx = rsize / ltm[0]
      dbiny = rsize / ltm[1]
  
      dxcorner = (dbinx - rsize) - dbinx * ltv[0]
      dycorner = (dbiny - rsize) - dbiny * ltv[1]
  
      # Round off to the nearest integer.
      bin = (_nint(dbinx), _nint(dbiny))
      corner = (_nint(dxcorner), _nint(dycorner))
  
      return bin, corner
docs: Compute the corner location and pixel size in units
      of unbinned pixels.
  
      .. note:: Translated from ``calacs/lib/fromlt.c``.
  
      Parameters
      ----------
      rsize : int
          Reference pixel size. Usually 1.
  
      ltm, ltv : tuple of float
          See :func:`get_lt`.
  
      Returns
      -------
      bin : tuple of int
          Pixel size in X and Y.
  
      corner : tuple of int
          Corner of subarray in X and Y.