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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<pmset.h>
+include	<plio.h>
+
+.help PMRIO
+.nf ---------------------------------------------------------------------------
+PMRIO -- A small package used to provide a means for efficient random
+sampling (at the pixel level) of large PMIO masks.  In other words, if we have
+a large mask and want to determine the values of successive mask pixels at
+random locations in the mask, this package provides a more efficient means
+for doing so than calling a routine such as PM_GLPI.  The mask must already
+exist; means are not provided within this package for creating or editing
+masks, only for reading them.
+
+		 pmr = pmr_open (pm, plane, buflimit)
+		    pmr_setrect (pmr, x1,y1, x2,y2)
+	      mval = pmr_getpix (pmr, x, y)
+		      pmr_close (pmr)
+
+PMR_OPEN opens the indicated 2 dimensional plane of the N dimensional mask PM.
+Buffer space used to provide an efficient means of randomly sampling the mask
+will be kept to within approximately BUFLIMIT integer units of storage (the
+internal table used to sample the mask is type integer, so BUFLIMIT is the
+approximate number of entries in the table).  Random sampling of the mask is
+provided by the integer function PMR_GETPIX, which returns the mask value at
+the point [i,j] within the specified plane.  PMR_SETRECT may be called before
+calling PMR_GETPIX to set the clipping rectangle, which defaults to the
+boundaries of the mask.  If a PMR_GETPIX call references outside the clipping
+region, ERR will be returned as the mask value (normal mask values are >= 0).
+Use of a clipping region other than the boundaries of the full mask can avoid
+the need for redundant clipping operations in the client.  PMR_CLOSE should
+be called to free the PMRIO table space (which can be extensive) when no longer
+needed.
+
+This package is a front end to the PLRIO package in PLIO, which does all the
+real work.
+.endhelp ----------------------------------------------------------------------
+
+# The following definitions must agree with those in plio$plrio.x.
+define	PMR_PL		Memi[$1]		# backpointer to PLIO descriptor
+define	PMR_PLANE	Memi[$1+10+($2)-1]	# defines 2D plane in ND mask
+
+
+# PMR_OPEN -- Open a PMIO mask for random pixel access.  Provides efficient
+# random pixel level access to any size mask.  This is a 2-dimensional
+# operator, but can be used to sample any 2-dim plane of an N-dim mask.
+
+pointer procedure pmr_open (pl, plane, buflimit)
+
+pointer	pl			#I PMIO/PLIO descriptor
+int	plane[ARB]		#I 2-dim plane to be accessed
+int	buflimit		#I approximate table size, or 0 if don't care
+
+pointer	plr_open()
+include	"pmio.com"
+
+begin
+	if (PM_MAPXY(pl) == YES) {
+	    call imaplv (PM_REFIM(pl), plane, v1, PM_MAXDIM)
+	    return (plr_open (pl, v1, buflimit))
+	} else
+	    return (plr_open (pl, plane, buflimit))
+end
+
+
+# PMR_GETPIX -- Return the value of the given mask pixel, identified by the
+# 2-dim coordinates of the pixel relative to the plane of the N-dim mask
+# specified at open time.
+
+int procedure pmr_getpix (pmr, i, j)
+
+pointer	pmr			#I PMR descriptor
+int	i, j			#I plane-relative coordinates of pixel
+
+pointer	pl
+int	plr_getpix()
+include	"pmio.com"
+
+begin
+	pl = PMR_PL(pmr)
+	if (PM_MAPXY(pl) == YES) {
+	    PMR_PLANE(pmr,1) = i
+	    PMR_PLANE(pmr,2) = j
+	    call imaplv (PM_REFIM(pl), PMR_PLANE(pmr,1), v1, PM_MAXDIM)
+	    return (plr_getpix (pmr, v1[1], v1[2]))
+	} else
+	    return (plr_getpix (pmr, i, j))
+end
+
+
+# PMR_SETRECT -- Set the clipping region for PMR_GETPIX.
+
+procedure pmr_setrect (pmr, x1,y1, x2,y2)
+
+pointer	pmr			#I PMR descriptor
+int	x1,y1			#I lower left corner of region
+int	x2,y2			#I upper right corner of region
+
+pointer	pl
+include	"pmio.com"
+
+begin
+	pl = PMR_PL(pmr)
+        if (PM_MAPXY(pl) == YES) {
+	    call amovi (PMR_PLANE(pmr,1), v1, PM_MAXDIM)
+            v1[1] = x1;  v1[2] = y1
+            call imaplv (PM_REFIM(pl), v1, v2, PM_MAXDIM)
+
+	    call amovi (PMR_PLANE(pmr,1), v3, PM_MAXDIM)
+            v3[1] = x2;  v3[2] = y2
+            call imaplv (PM_REFIM(pl), v3, v4, PM_MAXDIM)
+
+	    call plr_setrect (pmr, v2[1],v2[2], v4[1],v4[2])
+	} else
+	    call plr_setrect (pmr, x1,y1, x2,y2)
+end
+
+
+# PMR_CLOSE -- Free a PMRIO descriptor.
+
+procedure pmr_close (pmr)
+
+pointer	pmr			#I PMR descriptor
+
+begin
+	call plr_close (pmr)
+end