[GRASS-user] r.colors- transparent, HSB color

Dwight Needels needels at translucida.com
Thu Mar 19 10:11:08 EDT 2009

Glynn Clements wrote:
> For integer maps, you can create a reclass map using r.reclass. This
> has much lower overhead than creating a complete new map with
> r.mapcalc.

That is exactly what I was looking for (thanks!).

Glynn Clements wrote:
> Are you talking about simply specifying colours in HSB, and keeping
> the internal data in RGB, or having interpolation performed in HSB
> space?
> The former wouldn't be particularly involved; just an extension to
> G_parse_color_rule(). OTOH, you can obtain this functionality by
> pre-processing the rules with a script.

I was thinking of all interpolations in HSB space. However your first  
option (calculating RGB values from specified HSB colors but  
continuing to work in RGB space) would meet my current need. In fact,  
that is exactly what I have been doing, but externally to GRASS  
because I don't know how to write the script for HSB => RGB  
conversion. I would find this capability to be a useful enhancement of  

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