Problem creating pseudocolors

[Axel Berg]

Hi everyone,

Could anyone help me with the following? I would like to visualize a
data set with 2D irregular positions and irregular connections
(triangles), and two position-dependent floating-point data array's. I
would like to create in DX an image displaying both variables in one 2D
picture. So for example with one color-dependent variable and one
saturation-dependent variable, or mapping a set of grey-scale colors
onto another color image (pseudocolors). So basically I would like to
combine two colored images (or one colored and one grey-scaled), or two
colormaps of different data with identical positions and connections.
However, the colormap doesn't seem to allow the use two data components,
one for hue and one for saturation. Likewise, I cannot use Overlay while
that module only allows data with a regular grid.
All suggestions are welcome.

Best regards,

Axel

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* Axel Berg
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Could anyone point me at a good archive of this newsgroup?

[DL.Gresh]

Axel Berg wrote:
>
> Hi everyone,
>
> Could anyone help me with the following? I would like to visualize a
> data set with 2D irregular positions and irregular connections
> (triangles), and two position-dependent floating-point data array's. I
> would like to create in DX an image displaying both variables in one 2D
> picture. So for example with one color-dependent variable and one
> saturation-dependent variable, or mapping a set of grey-scale colors
> onto another color image (pseudocolors). So basically I would like to
> combine two colored images (or one colored and one grey-scaled), or two
> colormaps of different data with identical positions and connections.
> However, the colormap doesn't seem to allow the use two data components,
> one for hue and one for saturation. Likewise, I cannot use Overlay while
> that module only allows data with a regular grid.
> All suggestions are welcome.
>
> Best regards,
>
> Axel
>

Have you looked at the sample /usr/lpp/dx/samples/programs/
AlternateVisualizations? It shows some things similar to
what you want to do.

To map one variable to color and one to saturation is
pretty easy. First convert your "color" data values to
the range 0 to 1 (which is red through green through blue
back to red). Similarly, convert your "saturation" data values
to run from 0 to 1 (white to fully saturated). Then pass
these two data arrays into Compute, with the expression
"[a, b, 1]", which will make a hsv array, where value has
been set to 1. Then run this through Convert, making sure that
the "addpoints" param is 0. This will convert your hsv values
to rgb. Then insert this into your field as a "colors" component.

Like I said, something very like this is done in the sample
AlternateVisualizations.net.