[GRASS-user] exploding a color table

[Hamish]

> Neil Best pisze:
> > Has anyone come up with a way to convert a streched
> color table for a
> > floating point map into a set of discrete colors?  I
> am thinking especially
> > of NDVI, so I would like to generate the list of 256
> colors along the NDVI
> > floating point stretch to use with the result of
> r.recode that I used to
> > convert my NDVI map to an integer map.  If I could
> properly set the color
> > table for that new map then I could maintain the
> symbolization within GRASS
> > rather than having to spew a list of 256 colors for a
> > Mapserver configuration.  Any thoughts?


Glynn already answered with r.what.color, here is how to automate that:

   seq 255 | r.what.color -i mapname


but I wonder, are you using the "r.colors color=ndvi" rules?
they look like this:

cat $GISBASE/etc/colors/ndvi
-1.0000 white
-0.3000 blue 
-0.2000 205 193 173
 0.0000 150 150 150
 0.1000 120 100 51
 0.3000 120 200 100
 0.4000 28 144 3
 0.6000  6 55  0
 0.8000 10 30 25
 1.0000  6 27  7


just substitute your new range for the -1.0 to 1.0 steps with "r.colors color=rules", as long as the recode was linear.


I think though that your easiest solution is to use NASA's 0-255 color rules. :)
  http://oceancolor.gsfc.nasa.gov/DOCS/palette_ndvi.txt
  http://oceancolor.gsfc.nasa.gov/PRODUCTS/colorbars.html

you might be able to pipe those directly into r.colors or use them with "r.colors rules=palette_ndvi.txt".

see also  http://grass.osgeo.org/wiki/MODIS#Set_colors


Hamish