artemp/mapnik — Issue #428: Polygons and "the problem of adjacent edges"
Author: artemp
Created: 2011-10-11 16:18:15+00:00
State: open
Labels: Core_Library

An inherent problem with rendering each feature using AA is that "ghost lines" can appear between polygons that share boundaries when no polygon outlines are used (e.g. no LineSymbolizer is applied). The expected result is seamless color between polygons with the same fill, but instead very small lines "shine" through based on the background color.

A balance of gamma correction or dilation of the polygons might be able to be applied (manual setting by user?) to mitigate this issue.

McSeem's explanation is here:
http://thread.gmane.org/gmane.comp.graphics.agg/2359/focus=2367

And a MapServer ticket describing the problem is here:
http://trac.osgeo.org/mapserver/ticket/2616