[GRASS-user] setting a color value to transparent

Veronica Andreo veroandreo at gmail.com
Sun Apr 25 07:56:01 PDT 2021

Hi Chris,

Would choosing the categories (cat values) of features you want displayed
help? AFAIU from the ps.map manual, it is possible to select cats to be
displayed. Also, there's the possibility to use a where clause.

Just out of curiosity: why are you still running GRASS 7.4? We are at 7.8.5
already with python 3 support and soon to release GRASS 8.0 ;)


El vie, 23 abr 2021 a las 20:19, Chris Bartolomei via grass-user (<
grass-user at lists.osgeo.org>) escribió:

> Good afternoon all,
> I have a polygon map with a handful of features, I've added a column I use
> for setting RGB values "RRR:GGG:BBB" to color them. I use three (3) colors
> - red, orange, and yellow - but I would like some of them to be transparent
> but I can't find anywhere in the manuals what the code would be for
> transparent. Searching Google-land I see there's an RGBa standard which can
> set tranparency but GRASS doesn't seem to support that. I've tried setting
> the value to NULL, to "", to "none", and tried "0:0:0:0" (RGBa) all to no
> avail ...
> I am using ps.map to create an image so the ps rules file tells GRASS to
> use the RGB column to define the colors ... I believe I'm stuck with this
> methodology for now.
> Am I going to have to select the features which I do want colored and make
> a new map with just those features? or do I have to remove the postscript
> command for the RGB column and create a color table then reset my category
> values to 1, 2, 3, or 4 using a color table something like:
>   nv white
>   1 red
>   2 orange
>   3 yellow
>   4 white
>   end
> I was hoping to avoid creating a color table and changing the category
> values as this map gets modified twice a day... It's running in GRASS 7.4
> on Linux ...
> Thanks and happy weekend!
> :)
> Chris
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