gdalwarp w/netCDF output forces nodata value of 0

[bnordgren]

Using gdalwarp to resample an input image and store the result in a netCDF file results in the nodata value being set to zero for formats NC4 and NC4C. Formats NC and NC2 seem to work as expected. In my case, the target nodata value is 255 and the data type is byte.

Bad:

gdalwarp -of netCDF -co FORMAT=NC4 ...
gdalwarp -of netCDF -co FORMAT=NC4C ... 

However, saving the results of the gdalwarp to geotiff format, then performing a separate gdal_translate to netCDF preserves the nodata value.

Good:

gdalwarp -of GTiff ... 
gdal_translate -of netCDF -co FORMAT=NC4 ...

Attempting to set the nodata value with -dstnodata 255 results in:

ERROR 1: netcdf error #-122 : NetCDF: Attempt to define fill value when data already exists. .

[Even Rouault]

In 41576:

gdalwarp: make sure to try to redefine the destination nodata value from the source nodata even if the newly created dataset has already set a default nodata value (refs #7245)

[Even Rouault]

In 41577:

netCDF: fix bad interaction of SetNoDataValue() and SetGeoTransform()/SetProjection() for NC4/NC4C modes (fixes #7245)

[Even Rouault]

I didn't quite reproduce your exact errors, but I did see issues fixed by above commits.

[Even Rouault]

In 41674:

netCDF: fix memory leak introduced in r41577 (trunk only, refs #7245)