[GRASSLIST:6976] Re: PS.MAP command -->overlay raster

Hamish hamish_nospam at yahoo.com
Wed Jun 1 19:35:10 EDT 2005

> > Im going to export some maps with the command ps.map. I need to
> > overlay  two different raster, but the command cant do it. The first
> > one is the DTM  (painted with its colors), the second one is a
> > binary raster (that contain  two value: null() & 1). I need a
> > command to overlay this two raster... i  can use r.mapcalc, but if i
> > use it i'll have to redefinite the color  table.... is there a
> > specific command to do what i said? Thanks....
> You could use r.patch. What is null in your overlay will be taken 
> transparent and filled with your DTM. In order for the color tables to
> be  preseved make sure that no same values are present in both your
> rasters -  i.e. if your DTM is 1-1000 then recode your overlay to
> start at 1001.
> That will make your DTM hard-overlayed. An effect of semi-transparency
> you  could achieve using r.his Your DTM should be the hue, overlay
> should be the  intensity, saturation you can omit. Use r.composite to
> compose the output  back into a color Grass layer and enjoy (slight
> lose of quality as "only"  32768 colors is a practical [maximum] for
> Grass) or use 'rgb' command directly  in ps.map (for best quality).

I'm not sure exactly what Luca wants here, but in this situation, why
not just use a raster MASK?

g.copy binary_map,MASK
g.remove MASK

Or do you want semi-transparent "fields" overlaying the DTM?
not sure how to do that. Maybe v.to.rast and then overlay the 
vector area.


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