def _parse_crg_segment(self, fptr):
        """Parse the CRG marker segment.

        Parameters
        ----------
        fptr : file
            Open file object.

        Returns
        -------
        CRGSegment
            The current CRG segment.
        """
        offset = fptr.tell() - 2

        read_buffer = fptr.read(2)
        length, = struct.unpack('>H', read_buffer)

        read_buffer = fptr.read(4 * self._csiz)
        data = struct.unpack('>' + 'HH' * self._csiz, read_buffer)
        xcrg = data[0::2]
        ycrg = data[1::2]

        return CRGsegment(xcrg, ycrg, length, offset)