Re: converting HSV to RGB

• To: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>
• Subject: Re: converting HSV to RGB
• From: phorisb@xxxxxxxxxxxx (Patrick Horisberger)
• Date: Mon, 14 Aug 2000 23:08:54 +0200 (MET DST)

Thank you Bill for your promt response. 

I still try to understand the principles of VisAD. That's the reason why I
have got further basic questions.

I want to put two indepented variables on the same 2D display. The
ScalarMap to Display.Hue is used to represent the expection- and the
ScalarMap to Display.Saturation  is used to represent the error
values. As I've written in my last mail I want to convert this HSV values
back to RGB. How can I generate the arrays of HSV values without using the
Display.HSV ? Or is there another solution to pass the values to the
toReference() method ?

Patrick 

On Mon, 14 Aug 2000, Bill Hibbard wrote:

> Hi Patrick,
> 
> > 1. In the BaseColorControl class there is a method for initializing RGB
> > colormap to HSV Values. Now, is it possible to convert the HSV values
> > back to RGB again ?
> 
> The toReference() method of visad/HSVCoordinateSystem.java
> converts arrays of HSV values to arrays of RGB values.
> 
> > 2. I also have got  problems with the getTable method. After defining the
> > display as follows, the getTable() methods return a NullPointerException.
> 
> The problem is that ScalarMaps to Hue and Saturation do
> not generate any Controls, so getControl() returns null.
> The mapping from exp to Hue is linear and controlled by
> setRange() calls on the ScalarMap itself.
> 
> A ScalarMap to Display.HSV will generate a ColorControl,
> which controls the mapping from RealType values to Hue,
> Saturation and Value.
> 
> > ...
> > ...
> > 
> > ScalarMap colMap = new ScalarMap(col, Display.XAxis);
> > ScalarMap rowMap = new ScalarMap(row, Display.YAxis);
> > ScalarMap expMap = new ScalarMap(exp, Display.Hue);
> > ScalarMap errMap = new ScalarMap(err, Display.Saturation);
> > ConstantMap constMap = new ConstantMap(1.0f, Display.Value);
> > 
> > display.addMap(colMap);
> > display.addMap(rowMap);
> > display.addMap(expMap);
> > display.addMap(errMap);
> > display.addMap(constMap);
> > 
> > ..
> > ..
> > 
> > ColorControl saturationControl = (ColorControl)errMap.getControl();
> > float[][] saturation = saturationControl.getTable();
> > 
> > ColorControl hueControl = (ColorControl)expMap.getControl();
> > float[][] hue = hueControl.getTable();
> 
> ----------------------------------------------------------
> Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
> hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
> http://www.ssec.wisc.edu/~billh/vis.html
> 

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