[gdal-dev] Fwd: Re: gdal_calc.py and NoData issues

[Andreas Neumann]

forgot to send this to the list. Sorry.

see below:

-------- Originalnachricht --------
Betreff: Re: [gdal-dev] gdal_calc.py and NoData issues
Datum: 2014-11-19 14:16
Von: Andreas Neumann <a.neumann at carto.net>
An: Even Rouault <even.rouault at spatialys.com>

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 
;-(

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
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