[Qgis-developer] Processing with raster files > 4GB

[Andreas Neumann]

Hi,

I will have to do further testing about GRASS. On Windows (OSGeo4W 
install) it does not work too well. It probably works better on Linux.

The gdal_calc.py solution works very fast though - glad that we came to 
this solution!

Andreas

On 19.11.2014 11:25, G. Allegri wrote:
> And do you have problems with GRASS (directly, not through Processing)?
> In GRASS7 you can even drectly write to Geotiff without passing 
> through the internal format 
> (http://grass.osgeo.org/grass70/manuals/r.external.out.html).
> If GDAL is built with bigtiff support there souldn't be problems...
>
> giovanni
>
> 2014-11-19 10:44 GMT+01:00 Andreas Neumann <a.neumann at carto.net 
> <mailto:a.neumann at carto.net>>:
>
>     Hi Giovanni,
>
>     I need to change all pixels that have the value of 249 to a value
>     of 255. All other pixels should stay at their value.
>
>     Andreas
>
>     Am 2014-11-19 10:21, schrieb G. Allegri:
>
>             From my grayscale tiff images I want to replace one pixel
>             value
>
>         (249) with white (255). All other pixels should stay at the
>         value they
>         have.
>          >
>          > I came across https://github.com/chiatt/gdal_reclassify [1]
>         - but
>         this reclassifies all pixels, not only selected ones.
>          >
>          > Maybe I could use http://www.gdal.org/gdal_calc.html [2] with a
>         conditional syntax?
>
>         Hi Andreas, do you need to change the value of one specific pixel
>         only? I mean the pixel at [x,y] index?
>
>         giovanni
>
>
>          > Thanks,
>          > Andreas
>          >
>          > Am 2014-11-19 09:10, schrieb Carlos López PSIG:
>          >>
>          >> Hi Andreas,
>          >>
>          >> I also had problems to reclassify BIGTIFF with SAGA and GRASS!
>          >> Finally I used GDAL!
>          >>
>          >> Best regards,
>          >>
>          >>  [2]
>          >>
>          >> CARLOS LÓPEZ QUINTANILLA
>          >>
>          >> www.psig.es <http://www.psig.es> [3] [2]
>
>          >>
>          >> carlos.lopez at psig.es <mailto:carlos.lopez at psig.es>
>          >> +34 699.680.261 <tel:%2B34%20699.680.261>
>          >>
>          >> 2014-11-19 9:05 GMT+01:00 Andreas Neumann
>         <a.neumann at carto.net <mailto:a.neumann at carto.net>>:
>          >>
>          >>> Hi,
>          >>>
>          >>> I tried various tools, e.g.
>          >>>
>          >>> * SAGA reclassify
>          >>> * GRASS r.mapcalc
>          >>>
>          >>> Both work fine on smaller data sets, but fail on big data
>         sets.
>          >>>
>          >>> This is on Win7 64bit, with the OSGeo4W installer. I have
>         8gb RAM
>          >>> and 40GB disk free on C:, more free space on other disks
>         where
>         the
>          >>> data resides.
>          >>>
>          >>> I am not totally sure if it is the Bigtiff issue or some
>         other
>          >>> issue. It is just a guess that maybe I am hitting a limit
>         with
>         tiff.
>          >>> It is not fully transparent to me what Processing is
>         doing in the
>          >>> background (what file formats with what options it creates).
>          >>>
>          >>> It may also be an issue with SAGA or GRASS directly.
>          >>>
>          >>> Thanks if you know anything,
>          >>> Andreas
>          >>>
>          >>> Am 2014-11-18 21:15, schrieb Giovanni Manghi:
>          >>>
>          >>> Hi,
>          >>>
>          >>> I am having a lot of troubles with large raster files and
>          >>> processing.
>          >>>
>          >>> The intermediate results can go >4GB. Processing stops
>         with not
>         so
>          >>> helpful error messages.
>          >>>
>          >>> I wonder if processing is hitting the 4GB limit. Can I force
>          >>> processing
>          >>> to use the BIGTIFF option or a raster format that can
>         handle >4GB
>          >>> files?
>          >>>
>          >>> Hi Andreas, what tool specifically?
>          >>>
>          >>> cheers
>          >>>
>          >>> -- Giovanni --
>          >>> _______________________________________________
>          >>> Qgis-developer mailing list
>          >>> Qgis-developer at lists.osgeo.org
>         <mailto:Qgis-developer at lists.osgeo.org>
>          >>> http://lists.osgeo.org/mailman/listinfo/qgis-developer
>         [4] [1]
>          >>
>          >>  _______________________________________________
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>         <mailto:Qgis-developer at lists.osgeo.org>
>          >> http://lists.osgeo.org/mailman/listinfo/qgis-developer [4] [1]
>          >>
>          >>
>          >>
>          >> Links:
>          >> ------
>          >> [1] http://lists.osgeo.org/mailman/listinfo/qgis-developer [4]
>          >> [2] http://www.psig.es [3]
>          >
>          > _______________________________________________
>          > Qgis-developer mailing list
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>         <mailto:Qgis-developer at lists.osgeo.org>
>          > http://lists.osgeo.org/mailman/listinfo/qgis-developer [4]
>
>         Links:
>         ------
>         [1] https://github.com/chiatt/gdal_reclassify
>         [2] http://www.gdal.org/gdal_calc.html
>         [3] http://www.psig.es
>         [4] http://lists.osgeo.org/mailman/listinfo/qgis-developer
>
>
>
>
> -- 
> Giovanni Allegri
> http://about.me/giovanniallegri
> Twitter: https://twitter.com/_giohappy_
> blog: http://blog.spaziogis.it
> GEO+ geomatica in Italia http://bit.ly/GEOplus

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