a couple of questions about ColorControl setFunction method

• To: visad <visad-list@xxxxxxxxxxxxx>
• Subject: a couple of questions about ColorControl setFunction method
• From: Donna L Gresh <gresh@xxxxxxxxxx>
• Date: Mon, 3 Feb 2003 09:24:29 -0500

Hi,
I'm using the setFunction method of ColorControl to set a custom color map.
This mostly works, but I have a couple of questions. One is, is there a
simple way to "unset" the function (that is, to have it go back to the
default colormap)?  I tried naively setting the function to null but that
did not work.  I want to allow the user to choose between several
colormaps, including the default. I know I can build a custom map that
looks like the default, but wanted to avoid that.

Second, I use a FlatField to represent the colormap, which gets passed to
the setFunction method, with it constructed like this:

      RealType cp = RealType.getRealType("cp");
      RealType cr = RealType.getRealType("cr");
      RealType cg = RealType.getRealType("cg");
      RealType cb = RealType.getRealType("cb");
      try {
        RealTupleType crgb = new RealTupleType(cr, cg, cb);
        FunctionType colormapfunction = new FunctionType(cp, crgb);
        float[][] cpos = new float[1][pos.size()];
        for (int i=0; i<pos.size(); i++) {
          cpos[0][i] = pos.get(i);
        }

        Irregular1DSet colorbarpos = new Irregular1DSet(cp, cpos);

        FlatField mycolormap = new FlatField(colormapfunction,
colorbarpos);
        double[][] samples = new double[3][colors.size()];
        ColorRGBValue col;
        for (int i=0; i<colors.size(); i++) {
           col = colors.get(i);
           samples[0][i] = col.r;
           samples[1][i] = col.g;
           samples[2][i] = col.b;
        }

      mycolormap.setSamples(samples);


"pos" and "colors" are simply Java Vectors holding the 1D positons of the
colormap or the 3D rgb colors of the map.  It seems that this creates a
segmented colormap, in that there are abrupt boundaries between the colors,
instead of smooth. Is this how it works? i.e. do I have to have lots of
points in my colormap to get a smooth appearance?

Thanks for any help,
Donna

Donna L. Gresh, Ph.D.
IBM T.J. Watson Research Center
(914) 945-2472
http://www.research.ibm.com/people/g/donnagresh
gresh@xxxxxxxxxx

• Follow-Ups:
  • Re: a couple of questions about ColorControl setFunction method
    • From: Bill Hibbard