[Qgis-user] null values and color table from grass rasters

[Patrick Giraudoux]

Le 30/08/2012 17:30, Patrick Giraudoux a écrit :
> Hi,
>
> I am working with QGIS 1.8.0 lisboa, and have imported a raster into 
> GRASS 6.4.2 via the QGIS interface (it was a  TIF file originally).
>
> To my surprise null values are not displayed "transparent" in QGIS but 
> at the equivalent of zero in the coloramp.  However, I have checked 
> that the values of the cells are really "null" when pointed on with 
> the appropriate tool.
>
> When displayed within GRASS (tcltk interface) everything is OK and 
> null is transparent.
>
> Any idea about what happens?
>
> Patrick
>
>

Multiplying the raster by 1.0 in grass (r.mapcalc) solved the problem. 
The new map now has null values recognised by QGIS and so displayed 
transparent.