[Qgis-user] TIFF style problem

[Milena Nowotarska]

Hi Borys,

2010/6/11 Borys Jurgiel <borysiasty at aster.pl>:
>> @Borys: it might be related to #2491, but in this case transparency
>> works. I am in this good situation, that on my maps no data is white,
>> so setting transparency do them no harm.
>
> Unless you have white pixels within the data area :p

But of course I do; since I cope mostly with topo maps - it is useful
to have transparency for white pixels

>> @Błażej: you can also edit black areas with any non-gis-related raster
>> tool, set them white and then open in QGIS and set transparency. Just
>> an old trick ;)
>
> It's not a solution, it's heresy ;)) Nodata means nodata and nothing else. For
> formats not supporting nodata (like geoTIFF) there are two workarounds and
> both should work.

ok :) it just worked for me and mapinfo years ago but I cannot recall
if these were geotiffs or tiffs

> One of them is adding the alpha channel and setting it to 0, the second is to
> choose any non used value as the representative of nodata. If Błażej's files
> have "0" value used for both nodata and some data, I suppose there is also the
> alpha channel used and it should be handled by qgis.
>
> But it isn't and we could fix it. Looks like a good start for you to work with
> cpp issues. Just set up the compile environment in the end :p

no idea if that's qgis or gdal issue though...

Milena

-- 
Milena Nowotarska
http://wiki.osgeo.org/wiki/Milena_Nowotarska
http://quantum-gis.pl/