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diff --git a/pkg/images/tv/display/maxmin.x b/pkg/images/tv/display/maxmin.x
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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<mach.h>
+include	<imhdr.h>
+include	"iis.h"
+
+# MAXMIN -- Get the minimum and maximum pixel values of an image.  If valid
+# header values are available they are used, otherwise the image is sampled
+# on an even grid and the min and max values of this sample are returned.
+
+procedure maxmin (im, zmin, zmax, nsample_lines)
+
+pointer	im
+real	zmin, zmax		# min and max intensity values
+int	nsample_lines		# amount of image to sample
+
+int	step, ncols, nlines, sample_size, imlines, i
+real	minval, maxval
+pointer	imgl2r()
+include	"iis.com"
+
+begin
+	# Only calculate minimum, maximum pixel values if the current
+	# values are unknown, or if the image was modified since the
+	# old values were computed.
+
+	ncols  = IM_LEN(im,1)
+	nlines = IM_LEN(im,2)
+
+	if (IM_LIMTIME(im) >= IM_MTIME(im)) {
+	    # Use min and max values in image header if they are up to date.
+	    zmin = IM_MIN(im)
+	    zmax = IM_MAX(im)
+
+	} else {
+	    zmin = MAX_REAL
+	    zmax = -MAX_REAL
+
+	    # Try to include a constant number of pixels in the sample
+	    # regardless of the image size.  The entire image is used if we
+	    # have a small image, and at least sample_lines lines are read
+	    # if we have a large image.
+
+	    sample_size = iis_xdim * nsample_lines
+	    imlines = min(nlines, max(nsample_lines, sample_size / ncols))
+	    step = nlines / (imlines + 1)
+
+	    do i = 1 + step, nlines, max (1, step) {
+		call alimr (Memr[imgl2r(im,i)], ncols, minval, maxval)
+		zmin = min (zmin, minval)
+		zmax = max (zmax, maxval)
+	    }
+	}
+end