Hi,
I was able to do my color replacements with gdal_calc.py. It works fast
and efficient.
Here is my syntax:
gdal_calc.py -A image.tif --outfile=image_output.tif
--calc="(A==249)*255+(A!=249)*A"
Syntax looks similar to the QGIS raster calculator - but as opposed to
the QGIS raster calculator it actually works!
I will still continue to find out about SAGA. Maybe directly converting
from TIFF to SAGA before processing files in SAGA.
I believe that the QGIS raster calculator would need some developer love
- to make it more robust and easier to use ;-)
I am also pretty sure that the Processing integration of GRASS/SAGA does
not work well with big files - at least on Windows and when TIFF files
are used.
Thanks to all who helped!
Andreas
Am 2014-11-19 11:01, schrieb Carlos López PSIG:
Hi Andreas,
Yes, you can use gdal_calc.py
Certainly you need to perform several processes, but are very fast!
Be careful with bands!
Perhaps you will want to separate them.
Ciao,
[3]
CARLOS LÓPEZ QUINTANILLA
www.psig.es [3]
carlos.lo...@psig.es
+34 699.680.261
2014-11-19 9:26 GMT+01:00 Andreas Neumann <a.neum...@carto.net>:
Hi Carlos,
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 [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?
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 [4]
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 --
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Links:
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Links:
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[1] https://github.com/chiatt/gdal_reclassify
[2] http://www.gdal.org/gdal_calc.html
[3] http://www.psig.es
[4] tel:%2B34%20699.680.261
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