[gdal-dev] NoData value used during unscale in gdal_translate
even.rouault at mines-paris.org
Sat Nov 12 08:26:59 EST 2011
Le samedi 12 novembre 2011 02:48:16, Trent M Hare a écrit :
> It appears when using "-unscale" during a gdal_translate conversion,
> the defined NoData value is used when the offset/scale are applied. Not
> sure if this is intentional?
I also do not consider the current behaviour as the most intuitive one.
There's an old ticket http://trac.osgeo.org/gdal/ticket/3085 that deals with
that issue. I would be very tempted to apply (a variation of) the patch I had
attached to the ticket, that would honour the nodata value of the source band
if it exists. Perhaps only restricted to the -scale / -unscale case where this
is the most problematic, in order to limit backward compatibility issues when
only -a_nodata is used (pure remapping of nodata values can be done with
gdalwarp). The -srcnodata option I had proposed in the patch could also be
removed : if people have a dataset with a nodata value set that they want to
be considered as a regular value, they can preprocess it with a
"gdal_translate src.tif without_no_data.vrt -a_nodata none -of VRT" to unset
it, and use that intermediate dataset as the source for the gdal_translate -
What is your current opinion on this issue ?
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