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

[Roy]

Hi Andreas,

you can surely try to import the raster directly into GRASS in a 64bit 
linux,
very often this overcome memory issues, and use mapcalc sintiax,
something like:

reclassed_raster = if(original_raster == 249,255,original_raster)

regards,

Roy.

>
> GDAL would be my first choice - because it easy to automate. However, 
> I don't know how can do my task with GDAL.
>
> 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 - but this 
> reclassifies all pixels, not only selected ones.
>
> Maybe I could use http://www.gdal.org/gdal_calc.html with a 
> conditional syntax?
>
> 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 [2]
>> carlos.lopez at psig.es
>> +34 699.680.261
>>
>> 2014-11-19 9:05 GMT+01:00 Andreas Neumann <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
>>> http://lists.osgeo.org/mailman/listinfo/qgis-developer [1]
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