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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
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