No data value in Raster Merge not working

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No data value in Raster Merge not working

hksolanki
Dear List,

In QGIS1.8, when used 'No data value' checked in Raster menu> Miscellaneous>Merge, it showed always a message upto last version in 1.8 series.

"The process crashed some time after starting successfully"

In QGIS2.0.1 also, a window 'qgis-bin' appears constantly without result.

In Raster>Extraction>Clipper 'No data value' works fine in QGIS1.8 and QGIS2.0 both.

Using win7/32bit

Regards



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Re: No data value in Raster Merge not working

hksolanki
Correction!
Even after these message/behavior, results come in the target path/name, but with black color in no data areas.
Regards




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Re: No data value in Raster Merge not working

hksolanki
Dear List!
Has this discussion made previously in list or I am wrong at my point described?
or communication gap due to poor English?

I want to repeat:
If we use 'No data value' as zero by selecting the check box in Raster>Miscellaneous>Merge operation, it gives black color in no data region of output image. We can temporarily see the no data portions transparent by putting 'Additional no data value as zero in layer Properties>Transparency but after removing it from project whenever image is loaded again, it gives blackish no data areas.
 
In Raster>Extraction>clipper operation it works fine and no data areas in output image remains transparent/white always.

Using QGIS2.0.1 win7 32 bit

Regards



On Thu, Nov 28, 2013 at 6:38 PM, Harish <[hidden email]> wrote:
Correction!
Even after these message/behavior, results come in the target path/name, but with black color in no data areas.
Regards






--
Harish Kumar Solanki, Assistant Professor
National Institute of Rural Development (NIRD),
Ministry of Rural Development, Government of India
Jaipur, Rajasthan, India- Pin-302006

Geo_Coordinates (Office): 26.92162 N, 75.78921 E

Email- [hidden email], [hidden email],
Tele-Fax-0141-2209905, Mo.- 09214446732, 09414291732
Website-  http://www.nird.org.in, http://watershed.rajasthan.gov.in/
LinkedIn: www.linkedIn.com/in/hksolanki

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Re: No data value in Raster Merge not working

Etienne Tourigny-3
I can confirm that the target nodata values are set to zero (instead of "nodata").

This can be solved by adding -a_nodata <nodata> manually to the command, in which case the valeus are set to "nodata" and therefore transparent.

e.g. instead of 
gdal_merge.py -n 126 -of GTiff -o /data/src/qgis/qgis-master/tests/testdata/tmp1.tif /data/src/qgis/qgis-master/tests/testdata/landsat.tif
the command should be
gdal_merge.py -n 126 -a_nodata 126 -of GTiff -o /data/src/qgis/qgis-master/tests/testdata/tmp1.tif /data/src/qgis/qgis-master/tests/testdata/landsat.tif

Can you confirm this works for you? If so, I could fix this for future releases.
Although, there should probably be an option for this?

Etienne


On Fri, Dec 6, 2013 at 11:36 AM, Harish <[hidden email]> wrote:
Dear List!
Has this discussion made previously in list or I am wrong at my point described?
or communication gap due to poor English?

I want to repeat:
If we use 'No data value' as zero by selecting the check box in Raster>Miscellaneous>Merge operation, it gives black color in no data region of output image. We can temporarily see the no data portions transparent by putting 'Additional no data value as zero in layer Properties>Transparency but after removing it from project whenever image is loaded again, it gives blackish no data areas.
 
In Raster>Extraction>clipper operation it works fine and no data areas in output image remains transparent/white always.

Using QGIS2.0.1 win7 32 bit

Regards



On Thu, Nov 28, 2013 at 6:38 PM, Harish <[hidden email]> wrote:
Correction!
Even after these message/behavior, results come in the target path/name, but with black color in no data areas.
Regards






--
Harish Kumar Solanki, Assistant Professor
National Institute of Rural Development (NIRD),
Ministry of Rural Development, Government of India
Jaipur, Rajasthan, India- Pin-302006

Geo_Coordinates (Office): 26.92162 N, 75.78921 E

Email- [hidden email], [hidden email],
Tele-Fax-0141-2209905, Mo.- 09214446732, 09414291732
Website-  http://www.nird.org.in, http://watershed.rajasthan.gov.in/
LinkedIn: www.linkedIn.com/in/hksolanki

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Re: No data value in Raster Merge not working

hksolanki
I do not use commands/scripts in QGIS. I use only options available in corresponding window, there the option is available, which is not providing the desired output. But the same option in clipper window is giving correct results.
Regards

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Re: No data value in Raster Merge not working

Etienne Tourigny-3
In the window there is a box with the actual command used internally (at the bottom, just below "Load into canvas when finished)", it is easy to modify it after clicking the pencil button.

If you want this changed in future versions please test.

Etienne


On Fri, Dec 6, 2013 at 5:01 PM, Harish <[hidden email]> wrote:
I do not use commands/scripts in QGIS. I use only options available in corresponding window, there the option is available, which is not providing the desired output. But the same option in clipper window is giving correct results.
Regards


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Re: No data value in Raster Merge not working

hksolanki
For me it is OK, but I see QGIS reaching to desktop of real ground level practitioners who are not programmers or IT literate. They will not be able to bear the burden of window options and commands both. If your suggestion is up to next stable version it will be OK.  
Regards
Harish


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