[gdal-dev] gdal_calc.py and NoData issues

[Simen Langseth]

I saw the symbol <> first time in gdal calc what is meaning of it?

Thanks

On Wed, Nov 19, 2014 at 10:21 PM, Even Rouault <even.rouault at spatialys.com>
wrote:

> Le mercredi 19 novembre 2014 14:16:05, Andreas Neumann a écrit :
> > Hi Even,
> >
> > Thank you for trying to help. Unfortunately, the --overwrite option does
> > not help.
> >
> > I have a very small test file at http://webgis.uster.ch/temp/test.tif
> >
> > I used the following options:
> >
> > gdal_calc.py -A test.tif --overwrite --outfile=testcalc.tif
> > --calc="(A==249)*255+(A<>249)*A"
> >
> > All pixels with values of "255" are now "nodata" after running gdal_calc
> > ;-(
>
> I wrote "as well", so try with "--overwrite --nodata 99".
>
> >
> > May I please ask you to test/verify this?
> >
> > Thanks a lot!
> >
> > Andreas
> >
> > Am 2014-11-19 13:58, schrieb Even Rouault:
> > > 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
> > >> _______________________________________________
> > >> gdal-dev mailing list
> > >> gdal-dev at lists.osgeo.org
> > >> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>
>
>
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