[Plplot-general] RGB mapping for plsmap1

[Tune K. <ka...@sl...>]

Dear PLplot experts,

I have been using PLplot through python/numarray to plot
astronomical intensity maps in false color for 2 years.
Ever since I wrote the first shaded contour plot, I have
been wishing to improve the contrasts and the dynamic
range of the Hue mapping.  I came up with an inproved
mapping using RGB (can also be in HSV) by making
the function non0linear.  This requires many reference
points (eg. 20 points).

Following  the manual description on plshades and
the python example xw11.py, I wrote the following
cmap1_init_3D.  But it doesn't work.

I would appreciate any guidance or suggestion.

T. Kamae, Stanford Linear Accelerator Center.

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#   Color map 1 in RGB space for plot3D
#   (from plplot/examples/python/xw11.py)

    def cmap1_init_3D(self, gray):
        """Routine for defining a specific color map 1 in
        RGB space.  If gray is true, use basic grayscale
        variation from half-dark to light.  Otherwise use
        a parameteized mapping to R(z), G(z), and B(z) where
        z=[0,1].  i=0 corresponds to z=1.0, the brightest
        color for this implementation.
        """

        # Independent variable of control points.
        i = arange(0.0, 1.05, 0.05)
        if gray:
            # Red for control points.
            r = arange(241.0, 0.0, -12.0)
            # Green for control points.
            g = arange(241.0, 0.0, -12.0)
            # Blue for control points.
            b = arange(241.0, 0.0, -12.0)
        else:
            z=arange(1.0,1.05,0.05)
            z[20]=1.0
            # Red for control points.
            r = 113.9*sin(7.64*z**1.705+0.701)-916.1*(z+1.755)**1.862\
                +3587.9*z+2563.4
            rr = clip(r,0.0,255.0)
            # Green for control points.
            g = 70.0*sin(8.7*z**1.26-2.418)+151.7*z**0.5+70.0
            gg = clip(g,0.0,255.0)
            # Blue for control points.
            b = 194.5*z**2.88+99.72*exp(-77.24*(z-0.742)**2)\
                +45.40*z**0.089+10.0
            bb = clip(b,0.0,255.0)

        # Integer flag array is zero (no interpolation along far-side
        # of colour figure.)
        rev = array([0]+[1]*19+[0])
        # number of cmap1 colours is 256 in this case.
        # smaller the number of colours, the clearer the z contour
        #plscmap1n(256)
        plscmap1n(21)
        # Interpolate between control points to set up cmap1.
        plscmap1l(1, i, rr, gg, bb, rev)