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diff --git a/sys/imio/imbtran.x b/sys/imio/imbtran.x
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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<imhdr.h>
+include	<imset.h>
+include	<imio.h>
+
+# IMBTRAN -- Transform a point (x,y), possibly lying outside the boundary of
+# the N-dimensional image, back into the image using the current boundary
+# extension technique.
+
+procedure imbtran (im, v1, v2, ndim)
+
+pointer	im			# image descriptor
+long	v1[IM_MAXDIM]		# input, out of bounds point
+long	v2[IM_MAXDIM]		# transformed point (output)
+int	ndim			# number of dimensions to transform
+
+int	i
+long	vin, vmax
+
+begin
+	switch (IM_VTYBNDRY(im)) {
+	case BT_NEAREST:
+	    do i = 1, ndim {
+		vmax = IM_SVLEN(im,i)
+		vin  = v1[i]
+
+		if (vin < 1)
+		    v2[i] = 1
+		else if (vin > vmax)
+		    v2[i] = vmax
+		else
+		    v2[i] = vin
+	    }
+
+	case BT_REFLECT:
+	    do i = 1, ndim {
+		vmax = IM_SVLEN(im,i)
+		vin  = v1[i]
+
+		if (vin < 1)
+		    v2[i] = 1 + (1 - vin)
+		else if (vin > vmax)
+		    v2[i] = vmax - (vin - vmax)
+		else
+		    v2[i] = vin
+	    }
+
+	case BT_WRAP:
+	    do i = 1, ndim {
+		vmax = IM_SVLEN(im,i)
+		vin  = v1[i]
+
+		while (vin < 1)
+		    vin = vin + vmax
+		while (vin > vmax)
+		    vin = vin - vmax
+		v2[i] = vin
+	    }
+
+	default:
+	    do i = 1, ndim
+		v2[i] = v1[i]
+	}
+end