Bill,
That all worked great; thanks!
Donna L. Gresh, Ph.D.
IBM T.J. Watson Research Center
(914) 945-2472
http://www.research.ibm.com/people/g/donnagresh
gresh@xxxxxxxxxx
Bill Hibbard
<hibbard@facstaff.w To: Donna L
Gresh/Watson/IBM@IBMUS
isc.edu> cc: visad
<visad-list@xxxxxxxxxxxxx>
Sent by: Subject: Re: a couple of
questions about ColorControl setFunction method
owner-visad-list@ss
ec.wisc.edu
02/03/2003 10:20 AM
Hi Donna,
> 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.
You can call:
float[][] table
BaseColorControl.initTableVis5D(new float[3][tableLength]);
color_control.setTable(table);
to create the default color table of whatever length you like.
The call to setTable() will disable any Function passed to
setFunction().
> 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?
ColorControl samples Function values using
NEAREST_NEIGHBOR. Since this is essentially what
it does for a table, it seems to me that Function
should provide an alternative. So I changed it to
WEIGHTED_AVERAGE. Until the next VisAD release you
can find it at:
ftp://ftp.ssec.wisc.edu/pub/visad-2.0/untested/BaseColorControl.java
Please let us know if this does not solve you
problem.
Cheers,
Bill
