[geos-devel] [GEOS] #1064: Topology preserve simplify: unexpected behavior on similar polygons

GEOS geos-trac at osgeo.org
Fri Nov 27 10:40:38 PST 2020

#1064: Topology preserve simplify: unexpected behavior on similar polygons
 Reporter:  uclaros     |       Owner:  geos-devel@…
     Type:  defect      |      Status:  new
 Priority:  minor       |   Milestone:  3.9.0
Component:  Default     |     Version:  master
 Severity:  Unassigned  |  Resolution:
 Keywords:              |

Comment (by mdavis):

 Replying to [comment:2 strk]:
 > I guess one option here would be to pick the leftmost-upmost and the
 rightmost-bottommost points of a ring, split the ring in two parts, merge
 the lines which remain split by the origina vertex, then perform the
 simplification on the two parts and join them back togheter.
 > What do you think Martin ?

 I don't see how that works.  The problem with the current simplification
 algorithm is that it is essentially working on a line, not a ring - which
 is why it doesn't remove the endpoint even if it should be.  Doesn't
 splitting the ring just introduce one more endpoint?

 Not sure of what a solution could be ATM.  The simplification algorithm
 being used is Douglas-Peucker, and I don't know if that can be generalized
 to work on true rings.

Ticket URL: <https://trac.osgeo.org/geos/ticket/1064#comment:3>
GEOS <http://trac.osgeo.org/geos>
GEOS (Geometry Engine - Open Source) is a C++ port of the Java Topology Suite (JTS).

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