[QGIS-trac] Re: [Quantum GIS] #1963: "Ghost Lines" when using Anti-aliasing, polygons with shared boundaries, and no outline/QT::NoPen

[Quantum GIS]

#1963: "Ghost Lines" when using Anti-aliasing, polygons with shared boundaries,
and no outline/QT::NoPen
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   Reporter:  springmeyer                             |              Owner:  nobody       
       Type:  bug                                     |             Status:  new          
   Priority:  major: does not work as expected        |          Milestone:  Version 1.7.0
  Component:  MapCanvas                               |            Version:  Trunk        
   Keywords:  anti-aliasing,nopen,shared,polygons,2x  |   Platform_version:               
   Platform:  All                                     |           Must_fix:  No           
Status_info:  0                                       |  
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Comment(by springmeyer):

 We solved this sufficiently in Mapnik within the AGG renderer by allowing
 the user to control the AA gamma. A gamma of 0 is aliased while 1 is fully
 anti-aliased and setting gamma to around .6-.7 is able to remove the faint
 lines while keeping an AA-ish look with much more definition to edges
 (like coastlines) than can be achieved by the only other known workaround:
 overpainting with a thin line of the same color as the polygon fill. In
 short, we solved this by reducing the aggressiveness of the AA algorithm
 so that polygons are slightly dilated rather are fully AA or aliased.

 So, I assume that QT will expose somewhere an equivalent gamma setting (or
 partial AA ability) - as QT's renderer is originally based on AGG
 (http://labs.qt.nokia.com/2009/12/18/qt-graphics-and-performance-the-
 raster-engine/)

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Ticket URL: <http://trac.osgeo.org/qgis/ticket/1963#comment:7>
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