def getData(self,exten=None):
        """ Return just the data array from the specified extension
            fileutil is used instead of fits to account for non-
            FITS input images. openImage returns a fits object.
        """
        if exten.lower().find('sci') > -1:
            # For SCI extensions, the current file will have the data
            fname = self._filename
        else:
            # otherwise, the data being requested may need to come from a
            # separate file, as is the case with WFPC2 DQ data.
            #
            # convert exten to 'sci',extver to get the DQ info for that chip
            extn = exten.split(',')
            sci_chip = self._image[self.scienceExt,int(extn[1])]
            fname = sci_chip.dqfile

        extnum = self._interpretExten(exten)
        if self._image[extnum].data is None:
            if os.path.exists(fname):
                _image=fileutil.openImage(fname, clobber=False, memmap=False)
                _data=fileutil.getExtn(_image, extn=exten).data
                _image.close()
                del _image
                self._image[extnum].data = _data
            else:
                _data = None
        else:
            _data = self._image[extnum].data

        return _data
Return just the data array from the specified extension
            fileutil is used instead of fits to account for non-
            FITS input images. openImage returns a fits object.