[gdal-dev] gdal_calc.py and NoData issues

Even Rouault even.rouault at spatialys.com
Wed Nov 19 04:58:00 PST 2014

Le mercredi 19 novembre 2014 13:49:48, Andreas Neumann a écrit :
> Hi,
> I have an issue with gdal_calc.py and nodata values.
> My input data contains a lot of white pixels. After running gdal_calc.py
> with the following parameters
> gdal_calc.py -A test.tif --outfile=testcalc.tif
> --calc="(A==249)*255+(A<>249)*A"
> it turns out that all pixel values with 255 are now nodata values ;-( Is
> there an option so that my 255 values are not turned into nodata? I
> tested with the --NoDataValue option (e.g. 99 - which I don't use in the
> image), but it seems to be ignored. For me it is important that black
> and white pixels are preserved.

Use --overwrite as well, since otherwise the existing output file will be used 
to be just updated and not recreated.
It would be appropriate that the utility warns that --NoDataValue has no effect 
when the output file exists.

> Thanks for any hints,
> Andreas
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