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diff --git a/pkg/proto/vol/src/i2sun/trulut.x b/pkg/proto/vol/src/i2sun/trulut.x
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+include	<error.h>
+include	<ctype.h>
+include	"i2sun.h"
+
+# TR_ULUT -- Generates a look up table from data supplied by user.  The
+# data is read from a two column text file of intensity, greyscale values.
+# The input data are sorted, then mapped to the x range [0-4095].  A 
+# piecewise linear look up table of 4096 values is then constructed from 
+# the (x,y) pairs given.  A pointer to the look up table, as well as the z1 
+# and z2 intensity endpoints, is returned.
+
+procedure tr_ulut (fname, z1, z2, lut)
+
+char	fname[SZ_FNAME]		# Name of file with intensity, greyscale values
+real	z1			# Intensity mapped to minimum gs value
+real	z2			# Intensity mapped to maximum gs value
+pointer	lut			# Look up table - pointer is returned
+
+pointer	sp, x, y
+int	nvalues, i, j, x1, x2, y1
+real	delta_gs, delta_xv, slope
+errchk	ds_rlut, ds_sort, malloc		
+
+begin
+	call smark (sp)
+	call salloc (x, U_MAXPTS, TY_REAL)	
+	call salloc (y, U_MAXPTS, TY_REAL)
+
+	# Read intensities and greyscales from the user's input file.  The
+	# intensity range is then mapped into a standard range and the 
+	# values sorted.
+
+	call ds_rlut (fname, Memr[x], Memr[y], nvalues)
+	call alimr (Memr[x], nvalues, z1, z2)
+	call amapr (Memr[x], Memr[x], nvalues, z1, z2, real(U_Z1), real(U_Z2))
+	call ds_sort (Memr[x], Memr[y], nvalues)
+
+	# Fill lut in straight line segments - piecewise linear
+	call malloc (lut, U_MAXPTS, TY_SHORT)	
+	do i = 1, nvalues-1 {
+	    delta_gs = Memr[y+i] - Memr[y+i-1]
+	    delta_xv = Memr[x+i] - Memr[x+i-1]
+	    slope = delta_gs / delta_xv
+	    x1 = int (Memr[x+i-1]) 
+	    x2 = int (Memr[x+i])
+	    y1 = int (Memr[y+i-1])
+	    do j = x1, x2
+		Mems[lut+j] = y1 + slope * (j-x1)
+	}
+	Mems[lut+U_MAXPTS-1] = y1 + (slope * U_Z2)
+
+	call sfree (sp)
+end
+
+
+# DS_RLUT -- Read text file of x, y, values.
+
+procedure ds_rlut (utab, x, y, nvalues)
+
+char	utab[SZ_FNAME]		# Name of list file
+real	x[U_MAXPTS]		# Array of x values, filled on return
+real	y[U_MAXPTS]		# Array of y values, filled on return
+int	nvalues			# Number of values in x, y vectors - returned
+
+int	n, fd
+pointer	sp, lbuf, ip
+real	xval, yval
+int	getline(), open()
+errchk	open, sscan, getline, salloc
+
+begin
+	call smark (sp)
+	call salloc (lbuf, SZ_LINE, TY_CHAR)
+
+	iferr (fd = open (utab, READ_ONLY, TEXT_FILE))
+	    call error (1, "Error opening user lookup table")
+
+	n = 0
+	while (getline (fd, Memc[lbuf]) != EOF) {
+	    # Skip comment lines and blank lines.
+	    if (Memc[lbuf] == '#')
+		next
+	    for (ip=lbuf;  IS_WHITE(Memc[ip]);  ip=ip+1)
+		;
+	    if (Memc[ip] == '\n' || Memc[ip] == EOS)
+		next
+
+	    # Decode the points to be plotted.
+	    call sscan (Memc[ip])
+		call gargr (xval)
+		call gargr (yval)
+
+	    n = n + 1
+	    if (n > U_MAXPTS)
+	        call error (2,
+		    "Intensity transformation table cannot exceed 4096 values")
+
+	    x[n] = xval
+	    y[n] = yval
+	}
+
+	nvalues = n
+	call close (fd)
+	call sfree (sp)
+end
+
+
+# DS_SORT -- Bubble sort of paired arrays.  
+
+procedure ds_sort (xvals, yvals, nvals)
+
+real	xvals[nvals]		# Array of x values
+real	yvals[nvals]		# Array of y values
+int	nvals			# Number of values in each array
+
+int	i, j
+real	temp
+define	swap	{temp=$1;$1=$2;$2=temp}
+
+begin
+	for (i=nvals;  i > 1;  i=i-1)
+	    for (j=1;  j < i;  j=j+1) 
+		if (xvals[j] > xvals[j+1]) {
+		    # Out of order; exchange y values
+		    swap (xvals[j], xvals[j+1])
+		    swap (yvals[j], yvals[j+1])
+		}
+end