[GRASS-dev] ps.map: raster always under vector map?

[Markus Neteler]

On Mon, Apr 30, 2007 at 10:42:01AM +0100, Glynn Clements wrote:
> 
> Markus Neteler wrote:
> 
> > >>> Bear in mind that the raster map is always opaque, so it will obscure
> > >>> anything which is drawn beneath it.
> > >>>       
> > >> Markus:
> > >>     
> > >>> That's exactly what I need: in my case the raster map contains a few
> > >>> cells only, but I need it on top to not be covered by vector contour
> > >>> lines etc.
> > >>>       
> > >> ..
> > >>     
> > >>> Maybe ps.map's raster command needs an additional parameter "ontop" or
> > >>> something like this? Hacking C code as Hamish suggests might be asked
> > >>> too much for the average user.
> > >>>       
> > >> are the null areas solid white, not transparent?
> > >>     
> > >
> > > They are transparent. All fine.
> > Of course I was too hasty. Nothing fine.
> > > Just that the tons of contour
> > > lines cover the scarse raster areas in the raster maps. That's
> > > why I need them on top of the dense contour lines.
> > >   
> > ... and it seems that NULL is not respected by ps.map (as you will know
> > already).
> 
> For masked images, you need to use the one-operand form of the "image"
> operator with an image dictionary; see the RASTERMASK procedure in
> lib/psdriver/psdriver.ps for an example. This requires support for
> level 3 PostScript (present in GhostScript for a few years now; I
> don't know about printers).
> 
> Regarding the generation of the image data (ps/ps.map/ps_raster.c), a
> masked image needs 2 (mono) or 4 (RGB) components, with the mask byte
> first (i.e. AARRGGBB); see lib/psdriver/Raster.c.

I am afraid that I am not able to implement this.

Markus