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diff --git a/sys/vops/lz/amaps.x b/sys/vops/lz/amaps.x
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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+# AMAP -- Vector linear transformation.  Map the range of pixel values
+# a1,a2 from a into the range b1,b2 in b.  It is assumed that a1 < a2
+# and b1 < b2.
+
+procedure amaps (a, b, npix, a1, a2, b1, b2)
+
+short	a[ARB], b[ARB]
+short	a1, a2, b1, b2
+
+long	minout, maxout, aoff, boff, pixval
+
+real	scalar
+
+int	npix, i
+
+begin
+	    scalar = (real (b2) - real (b1)) / (real (a2) - real (a1))
+
+	minout = min (b1, b2)
+	maxout = max (b1, b2)
+	aoff = a1
+	boff = b1
+
+	do i = 1, npix {
+	    pixval = (a[i] - aoff) * scalar
+	    b[i] = max(minout, min(maxout, pixval + boff))
+	}
+end