[Gdal-dev] transparency

[ivan marchesini]

Hi to all,
I need to solve this problem, please help me..
some people who are really new to gis, and particularly to qgis, must
simply load two 0/1 (white and black) raster maps and print... they
should print a lot of maps using this method...
the problem is that at the boundary between two maps (where there is the
overlay) they have the superimposition of the white border of a map over
the other map... so they obtain a white strip at the junction between
the two maps..
It would be useful if the white pixel became transparent and the black
pixels remained black....
is there a simple way, using gdal to convert the maps before to load
them into qgis, in a way that they will appear (into qgis) black along
the lines of the maps and null (transparent) in the white area???
I think it is something like adding an alpha channel??

maybe it is a stupid question... 
 sorry...


thanks 

Ivan

-- 
Ivan Marchesini
Department of Civil and Environmental Engineering
University of Perugia
Via G. Duranti 93/a 
06125
Perugia (Italy)
e-mail: marchesini at unipg.it
        ivan.marchesini at gmail.com
tel: +39(0)755853760
fax: +39(0)755853756
jabber: geoivan73 at jabber.org