Hi Carlos,
I reprojected to a different swiss projection system and the expression
still does not work. I tested various projections, including UTM-32N.
Very strange ...
There clearly seems to be a bug in the raster calculator. I will open a
bug with high priority.
Thanks for testing and helping!
Andreas
Am 2014-11-18 15:36, schrieb Carlos Cerdán:
Hi Andreas:
It is solved: you have to reproject your TEMP layer. I've tried with
UTM-32N zone and raster calculator works fine.
Why raster calculator (and SAGA) doesn't work with your original CRS?
Well, I don't know, perhaps devs group have the answer.
It was a good challenge.
Carlos
2014-11-18 4:37 GMT-05:00 Andreas Neumann <[email protected]>:
Hi Carlos,
Thank you for your help!
I tried with
(TEMP@1=249)*255 + (TEMP@1<249)*TEMP@1 + (TEMP@1>249)*TEMP@1
My layer is called "temp". However, the resulting file contains all
0.
I tried in both QGIS 2.4 and 2.6.
Is there something wrong with the input file? It was generated from
a PDF with ghostscript. Here is the metadata:
-----
GDAL provider
GTiff
GeoTIFF
Datensatzbeschreibung
//gis/gis/mapserverdata/uep/release_2014_11/temp.tif
TIFFTAG_DATETIME=2014:11:17 09:50:08
TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)
TIFFTAG_SOFTWARE=GPL Ghostscript 9.10
TIFFTAG_XRESOLUTION=600
TIFFTAG_YRESOLUTION=600
Kanal 1
STATISTICS_MAXIMUM=255
STATISTICS_MEAN=247.18714741724
STATISTICS_MINIMUM=0
STATISTICS_STDDEV=37.198102288306
Dimensionen
X: 71575 Y: 70867 Kanäle: 1
Leerwert
*Leerwert nicht gesetzt*
Datentyp
Byte - Acht Bit vorzeichenlose Ganzzahl
Pyramidenübersichten
Räumliches Bezugssystem des Layers
+proj=somerc +lat_0=46.95240555555556 +lon_0=7.439583333333333
+k_0=1 +x_0=600000 +y_0=200000 +ellps=bessel
+towgs84=674.4,15.1,405.3,0,0,0,0 +units=m +no_defs
Layerausdehnung (in urspünglicher Projektion des Layers)
0.0000000000000000,-70867.0000000000000000 :
71575.0000000000000000,0.0000000000000000
Kanal
Kanal 1
Kanal Nr
1
Keine Statistik
Noch keine Statistik gesammelt
------------
Thanks again if you have any idea what may be wrong with my file or
the above listed raster calc statement.
Andreas
Am 2014-11-17 18:38, schrieb Carlos Cerdán:
Hi Andreas:
I think QGIS raster calculator can make this job. Conditional
syntax
is a little bit... different. The sentence that can do it is:
(TIFF=249)*255 + (TIFF<249)*TIFF + (TIFF>249)*TIFF
Where TIFF is your raster layer. The trick is: if the sentence in
parentheses is true, it gets value 1, else zero; so we have to
multiply by 255 to replace the 249 values. Next we have to add the
other values.
Good luck,
Carlos Cerdán
PD. Please let me know if i'm wrong with this suggestion
2014-11-17 12:02 GMT-05:00 Andreas Neumann <[email protected]>:
Hi,
I have a very simple task (at least I thought it is simple), but am
not able to do it properly.
I have a grayscale tiff value where I would like to replace the
value of 249 with 255 - all other values should stay as they are.
I tried with gdal "nearblack", but nothing changed - I started a
separate email-thread about that at the gdal list.
Then I tried with the QGIS raster calculator - but it does not
support conditional syntax.
I tried with Processing and GRASS - but it would stop at 8% - the
file is quite big.
Finally I came across SAGA "Reclassify with grid value". The
dialogue is very complicated and hard to understand. After a while
it would stop with an error message telling me that Saga may not be
properly configured - but it says that it is properly installed.
Quite confusing ...
I am trying on Win7 64bit.
If the file wouldn't be so big I would try this task in The Gimp -
where it is very simple to replace one pixel values with another -
using "Select by color" and "fill with a specific color".
Any idea how I could achieve my task with GDAL, QGIS, GRASS or
Saga?
Thanks,
Andreas
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