[GRASSLIST:2512] Re: alpha blending

[Glynn Clements]

francesco.pirotti wrote:

> I was wondering if  there is a trick or even a module which enables 
> transparency on a vector poligon (with rasters I guess you can use a trick 
> with the hue-saturation module).  I saw Radim's qgis implementation of 
> GRASS rasters and vectors, including alpha blending 
> (http://mpa.itc.it/radim/qgis/) so I was wandering if something similar 
> is/will be/might be implemented in GRASS

Nothing like that currently exists in the display architecture, and
isn't likely to be added any time soon.

The simplest solution is to convert everything to rasters, and either:

a) export the rasters to a standard image format (e.g. PPM), and use a
paint program (or image processing utilities such as pbmplus/netpbm)
to blend them,

b) use d.his or r.his, or

c) use r.mapcalc.

-- 
Glynn Clements <glynn.clements at virgin.net>