docs: def read_nih_image_header(fh, byteorder, dtype, count, offsetsize):
      """Read NIH_IMAGE_HEADER tag from file and return as dict."""
      a = fh.read_record(TIFF.NIH_IMAGE_HEADER, byteorder=byteorder)
      a = a.newbyteorder(byteorder)
      a = recarray2dict(a)
      a['XUnit'] = a['XUnit'][:a['XUnitSize']]
      a['UM'] = a['UM'][:a['UMsize']]
      return a