[QGIS-trac] Re: [Quantum GIS] #1945: [Vista] Qgis crashes removing GRASS raster layer from map canvas

[Quantum GIS]

#1945: [Vista] Qgis crashes removing GRASS raster layer from map canvas
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        Reporter:  juanelz                                    |         Owner:  rugginoso    
            Type:  bug                                        |        Status:  closed       
        Priority:  critical: causes crash or data corruption  |     Milestone:  Version 1.5.0
       Component:  GRASS                                      |       Version:  HEAD         
      Resolution:  fixed                                      |      Keywords:  GRASS rasters
Platform_version:  Vista                                      |      Platform:  Windows      
        Must_fix:  Yes                                        |   Status_info:  0            
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Comment (by lutra):

 Replying to [comment:29 rblazek]:

 > Its on you to find the difference causing the problem. Try various CT,
 pieces of raster etc.
 > And please test first if it renders well in pure GRASS! Such a test
 should always be done before an error is reported for QGIS!

 For what I see is just a visualization/render problem in qgis trunk, not
 in qgis 1.4 or GRASS osgeo4w (tested both before commenting). Have a look
 to the small test described below (use the attached "ancc6_geo.dem").


 * Import "ancc6_geo.dem" in a mapset with in qgis 1.4 or with GRASS, add
 it to the canvas and then it will render fine. Open the mapset in qgis
 trunk, add it to the canvas and it will render wrong.

 * You can also test otherwise. Import "ancc6_geo.dem" in qgis trunk, add
 it to the canvas and it will render wrong. Then open the mapset in qgis
 1.4 or GRASS, add it to the canvas and it will render fine.

 The bottom line seems to be the fact that in qgis trunk there are cases
 (always?) where the GRASS raster is added with the "wrong colorbands".

 See attached image "colorbands.png", and make a test using
 "ancc6_geo.dem":

 * create a project in qgis 1.4 and import in a mapset the raster
 "ancc6_geo.dem". Add it to the canvas. In the raster properties it will
 show as "single band gray". Save the project (leave the GRASS raster in
 the canvas/legend).

 * open the project in qgis trunk: the GRASS raster renders fine (and guess
 what, no "value tool" plugin errors). Now add it again from the GRASS
 toolabr or from the GRASS browser: it will render wrong. Open the raster
 properties and it will show as "three band color", but color bands are not
 set. Save the project (leave in the legend/canvas both the -same- raster
 added in 1.4 and trunk).

 * open again the project in qgis 1.4, the raster added in qgis trunk will
 not even show in the legend/canvas.


 I believe this is the key of the problem.


 > Please DON'T report the problems with valuetool here. I have explained
 why the problem cannot be fixed in GRASS provider. You can fill a ticket
 for enhancement of raster providers infrastructure. You can fix the
 valuetool to use only raster layer identify().


 Please don't get it wrong, I'm just noticing about the side effects of the
 new provider. In any case see the above test, it seems to me that it
 proves there is a problem in the provider when a GRASS raster is added
 into the canvas. Solve this also the plugin problem will be gone.



 > What do you mean by single band and multi band? GRASS rasters are always
 single band.


 forget about this and just consider the above steps to reproduce the
 problem. I thought to have found a pattern about the type of rasters to be
 imported into GRASS, but I was wrong.

-- 
Ticket URL: <https://trac.osgeo.org/qgis/ticket/1945#comment:30>
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