1 files changed, 36 insertions, 0 deletions
diff --git a/noao/twodspec/longslit/getdaxis.x b/noao/twodspec/longslit/getdaxis.x
new file mode 100644
index 00000000..06be22c7
--- /dev/null
+++ b/noao/twodspec/longslit/getdaxis.x
@@ -0,0 +1,36 @@
+include	<mwset.h>
+
+
+# GET_DAXIS -- Get logical dispersion axis.
+
+procedure get_daxis (im, laxis, paxis)
+
+pointer	im			#I IMIO pointer
+int	laxis			#O Logical dispersion axis
+int	paxis			#O Physical dispersion axis
+
+real	ltm[2,2], ltv[2]
+pointer	mw, tmp, mw_openim()
+int	imgeti(), clgeti()
+errchk	imaddi, mw_openim, mw_gltermr
+
+begin
+	# Get the dispersion axis from the header or package parameter.
+	iferr (paxis = imgeti (im, "dispaxis")) {
+	    paxis = clgeti ("dispaxis")
+	    call imaddi (im, "dispaxis", paxis)
+	}
+	laxis = paxis
+
+	# Check for a transposed image.
+	iferr {
+	    mw= NULL
+	    tmp = mw_openim (im); mw = tmp
+	    call mw_gltermr (mw, ltm, ltv, 2)
+	    if (ltm[1,1] == 0. && ltm[2,2] == 0)
+		laxis = mod (paxis, 2) + 1
+	} then
+	    ;
+	if (mw != NULL)
+	    call mw_close (mw)
+end