[gdal-dev] problem with dstnodata and vrt in gdalwarp

fabrice martin fabrice_martin2 at yahoo.fr
Fri Nov 23 15:19:35 EST 2007


Hello,

I have a problem using dstnodata when the input is a vrt file: it 
looks as if dstnodata is not taken into account. Indeed, if I choose destination coordinates that are not completely overlapped by the source images, nodata areas are 
always black, whatever the value for dstnodata.

For example, I create a simple vrt with gdal_vrtmerge: 
gdal_vrtmerge.py -o test.vrt *.tif

If I reproject this vrt, nodata 
areas are black:
gdalwarp -of Gtiff -te 897000 6657000 898000 6658000 -s_srs 
"EPSG:27582" -t_srs "EPSG:2154" -tps -rc -tr 0.5 0.5 -dstnodata 255 -co INTERLEAVE=PIXEL test.vrt test_with_vrt.tif

If I reprojet directly 
the same *.tif images, nodata areas are white as expected:
gdalwarp -of 
GTiff -te 897000 6657000 898000 6658000 -s_srs "EPSG:27582" -t_srs 
"EPSG:2154" -tps -rc -tr 0.5 0.5  -dstnodata 255  -co 
INTERLEAVE=PIXEL  
*.tif test_with_tifs.tif

Could you confirm the problem ? If so, do you have any 
insight on where to look in the code to correct it ?
Thank 
you,

Fabrice.




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