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 [3] [2]
 >>
 >> carlos.lo...@psig.es
 >> +34 699.680.261
 >>
 >> 2014-11-19 9:05 GMT+01:00 Andreas Neumann <a.neum...@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@lists.osgeo.org
 >>> http://lists.osgeo.org/mailman/listinfo/qgis-developer [4] [1]
 >>
 >>  _______________________________________________
 >>  Qgis-developer mailing list
 >>  Qgis-developer@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
 > Qgis-developer@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
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