[GRASSLIST:2929] Re: ps.map - only one raster??

Glynn Clements glynn.clements at virgin.net
Sat Mar 13 07:06:21 EST 2004

francesco.pirotti wrote:

> GRASS's module ps.map works really well, especially in 5.7 where it is 
> supported by a really nice GUI from d.m.
> Question 1:
> does it really permit to print any number of vectors but only ONE 
> raster?  What if I have two separate rasters to print?
> Question 2:  I seem to always have the vectors being drawn OVER my 
> raster... what if I want my raster on top of everything?

A raster will obscure all other maps (but not the title or legend), so
neither of the above is of much use.

> I know it is strange, but I have a black and white map where I have given 
> NULL value to the white parts thus giving it some "transparency" so that I 
> can draw poligon areas below it and see both the poligon and the map 
> characteristics over the same area (otherwise the poligon would totally 
> paint over my map).  But if I use ps.map it draws all my vectors on top of 
> my raster.
> Is there a way?  Tips welcome (even programming tips, I get around a little 
> with GRASS's C modules and tcl for d.m)

PostScript levels 1 and 2 don't support masked images, so you would
need a level 3 PostScript interpreter (Ghostscript 6.x and later have
level 3 support, but I don't know how common level 3 support is among

ps.map pre-dates level 3 PostScript; presently, ps.map only uses
levels 1 and 2, and its use of level 2 features doesn't go much beyond
colour images.

Adding masked image support probably wouldn't be a great deal of work. 
Most of the effort would be fixing assumptions that the level will be
either 1 or 2 (e.g. changing "PS.level == 2" to "PS.level >= 2" etc).

Glynn Clements <glynn.clements at virgin.net>

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