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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<gescape.h>
+include	<mach.h>
+include	<gim.h>
+include	<gki.h>
+
+# GIM_LOADCOLORMAP -- Load a colormap into the display (hardware) colormap.
+# Any number of colormaps may be defined, but only one may be loaded at a
+# time.  A linear transformation may optionally be applied to the (normalized)
+# colormap when it is loaded.  Set offset=0.5, slope=1.0 to load the colormap
+# without scaling.  A negative slope inverts the image.
+#
+# The offset refers to the center of the mapped region of the transfer
+# function, which is why the center value is at 0.5.  For example, if the
+# range of raster pixel intensities is normalized to the range 0.0 to 1.0,
+# then a transfer function of [offset=0.3,slope=3.0] will display the region
+# of intenstities centered around the normalized intenstity of 0.3, with a
+# contrast of 3.0 (the screen intensity changes 3 units for a unit change in
+# raster pixel intensity).  The transfer function [offset=0.3,slope=-3.0]
+# will display the same range of pixel intensitites, but with a negative
+# contrast.  The transfer function [offset=0.5,slope=1.0] has intercepts
+# of [0,0] and [1,1] hence it displays the full range of raster pixel
+# intensities - the input colormap is used as is, without resampling.
+
+procedure gim_loadcolormap (gp, colormap, offset, slope)
+
+pointer	gp			#I graphics descriptor
+int	colormap		#I colormap number (0 is display colormap)
+real	offset, slope		#I linear transformation on colormap
+
+real	veclen, scale
+short	gim[GIM_LOADCMAP_LEN]
+
+begin
+	scale = GIM_LOADCMAP_SCALE
+	gim[GIM_LOADCMAP_MP] = colormap
+	gim[GIM_LOADCMAP_OF] = ((GKI_MAXNDC + 1) / scale) *
+	    max(-scale, min(scale, offset))
+
+	if (abs(slope) < EPSILONR)
+	    veclen = GKI_MAXNDC
+	else {
+	    veclen = GKI_MAXNDC + 1
+	    veclen = min (veclen / 2, veclen / abs(slope) / 2)
+	}
+	gim[GIM_LOADCMAP_DX] = veclen
+	gim[GIM_LOADCMAP_DY] = veclen * slope
+
+	call gescape (gp, GIM_LOADCMAP, gim, GIM_LOADCMAP_LEN)
+end