[QGIS-trac] Re: [Quantum GIS] #1533: WMS raster transparency problem

[Quantum GIS]

#1533: WMS raster transparency problem
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        Reporter:  jctull                           |         Owner:  ersts                          
            Type:  bug                              |        Status:  assigned                       
        Priority:  minor: annoyance or enhancement  |     Milestone:  Version 1.0.1                  
       Component:  MapCanvas                        |       Version:  HEAD                           
      Resolution:                                   |      Keywords:  wms raster transparency refresh
Platform_version:  10.5.6                           |      Platform:  OS X                           
        Must_fix:  Yes                              |   Status_info:  0                              
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Changes (by ersts):

  * priority:  major: does not work as expected => minor: annoyance or
               enhancement
  * status:  new => assigned
  * owner:  nobody => ersts

Comment:

 This is a known issue. If you keep repeatedly hitting apply, the
 transparency it is additive. Likewise, if you decrease the transparency,
 it is still additive. However, if you pan the map canvas a little and
 cause a new fetch request, your layer will be at the correct/expected
 transparency level.

 It seems to be a bug in Qt with setting the alpha value for an image more
 than once. Each apply causes a refresh and thus a reapplication of the
 alpha value. Too speed things up, the WMS provider does not request a new
 version of the image if the extent has not changed, it uses a cached
 version.

 I am going to downgrade this a little, while it needs to get fixed but it
 does not cause a crash or a damage of data

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Ticket URL: <http://trac.osgeo.org/qgis/ticket/1533#comment:2>
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