Re: [Plplot-general] RGB mapping for plsmap1

[Curtis C. <cu...@hi...>]

I think the PLplot colormap setting functions expect color ranges clamped
between [0,1].

Cheers,
Curtis



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    *   Curtis S. Cooper, Graduate Research Assistant         *
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On Sat, 4 Dec 2004, Tune Kamae wrote:

> 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.
>
> ----------------------------------------------------------------------------
> #   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)
>
>
>
>
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