filename	IN:	Name of the HDF file
	ref	IN:	Reference number for next call to DFR8putimage or DFR8addimage

	Purpose	Specifies the reference number of the image to be written when DFR8addimage or DFR8putimage is next called.
	Return value	Returns SUCCEED (or 0) if successful and FAIL (or -1) otherwise.
	Description	It is unlikely that you will need this routine, but if you do, use it with caution. There is no guarantee that reference numbers appear in sequence in an HDF file; therefore, it is not safe to assume that a reference number is the index of an image. In addition, using an existing reference number will overwrite the existing 8-bit raster image data.

	FORTRAN	integer function d8wref(filename, ref)
		character*(*) filename
		integer ref