[Qgis-user] Raster - values and histogram

[Nicolas Cadieux]

Hi, 
I am not sure if there is a bug but since you have a virtual raster, I would look to see if they all have the same no data values.  Try loading only one raster or try saving the virtual raster as a tif  and setting the no data value.  Do you have the same problem?  
If Qgis does not recognize the no data value, it may be thrown out by trying to stretch the image from -32768 to whatever you have.  In that case, your raster will not be "viewed correctly" as it is trying to display more than 256 shades which is the max a screen can handle. In that case you would see only black and white. 
Hope this help! 
Nicolas 
On Apr 17, 2016 8:22 AM, "Lene Fischer [via OSGeo.org]" <ml-node+s1560n5261624h5 at n6.nabble.com> wrote: 

	







Hi, 
I´m rehearsing my lectures for tomorrow – and using 2.14.1 on windows. 
  
When I create a virtual raster the values are not viewed correct. Then I click Stretch Histogram to full data. Nothing happens. 
I have to go to properties and load to ‘min-max’ actual values before anything happens. 
  
If I use Properties >Histogram and try to Reset and then ReCompute histogram – nothing happens… 
  
What do I do wrong? 
  
A bit distressed – Giving lectures in raster QGIS tomorrow … 
Regard 
Lene Fischer 




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