[Gdal-dev] gdalwarp Transparency Question

[Reinaldo Escada Chohfi]

Hello,

I'm runing gdalwarp (FWTools 1.0.0a7) to mosaic geotiff images because the 
images are large and I run into memory problems with gdal_merge.

I get some strange results in several mosaics in the overlapping areas 
between images.  I use -srcnodata 0 to have gdalwarp do the transparency in 
these overlapping areas.

My question is, if am using -scrnodata 0, will the transparency be made 
when all 3 pixel values are 0, 0, 0 (RGB) or whenever any of the bands has 
a pixel value equal to 0?  It looks like I get a transparency only in the 
Blue, sometimes only in the Red or Green bands and the image has blue, red 
or green spots.  Do I have to use -scrnodata value "0 0 0" in order to get 
transparency only when RGB are equal to 0, 0, 0?

Thanks in advance for the help.

Reinaldo