[GRASS-user] Label difficulties

Glynn Clements glynn at gclements.plus.com
Wed Aug 29 00:42:29 EDT 2007

Adam Dershowitz wrote:

> > You might try ps.map or d.* commands directly on the command line,  
> > they
> > might not be as user friendly as the GUI, but they are more mature and
> > IM(biased)O ps.map creates the best looking output.
> But, for either using the PNG driver,  ps.map, or d.* commands I  
> can't seem to figure out how to combine two raster maps.  In other  
> words, what I am currently doing with the GUI, is displaying two  
> raster maps, one is 50% transparent, and then adding some vector  
> information over the top of that.  With the GUI I just set the opaque  
> to transparent slider for one of the maps.
> Is there a way to do the equivalent from the command line?  Or just  
> to overlay two maps, one at 50% opaque, to generate a new raster  
> map?  It seems like it should be easy, but I am not having any luck  
> figuring it out.  I did try g.pnmcomp, that the gui uses, but it  
> seems that it does  not find the files properly and it "isn't meant  
> for the end user" anyway.
> Any ideas?

Use g.pnmcomp, pnmcomp (from NetPBM) or GIMP (etc).

The input= and mask= arguments to g.pnmcomp refer to PPM/PGM files,
e.g. those produced by the PNG driver (despite its name, it can
produce either PNG, PPM/PGM or BMP files, depending upon the setting

You can blend two raster maps with r.blend, but that only makes sense
if you're already dealing with raster maps. If you want to blend
display output, use g.pnmcomp or an image-editing program.

Glynn Clements <glynn at gclements.plus.com>

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