8000 Add CascadedPolygonUnion bufferUnion by dr-jts · Pull Request #470 · locationtech/jts · GitHub
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Add CascadedPolygonUnion bufferUnion #470

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Merged
merged 2 commits into from
Sep 5, 2019
Merged

Add CascadedPolygonUnion bufferUnion #470

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8fecd45
Initial commit of CascadedPolygonUnion bufferUnion enhancement
dr-jts Aug 30, 2019
42a358d
Javadoc
dr-jts Sep 5, 2019
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30 changes: 28 additions & 2 deletions modules/core/src/main/java/org/locationtech/jts/operation/union/OverlapUnion.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.LineSegment;
import org.locationtech.jts.geom.TopologyException;
import org.locationtech.jts.geom.util.GeometryCombiner;

/**
Expand Down Expand Up @@ -196,10 +197,35 @@ private Geometry extractByEnvelope(Envelope env, Geometry geom,
}

private Geometry unionFull(Geometry geom0, Geometry geom1) {
Geometry union = geom0.union(geom1);
return union;
try {
return geom0.union(geom1);
}
catch (TopologyException ex) {
/**
* If the overlay union fails,
* try a buffer union, which often succeeds
*/
return unionBuffer(geom0, geom1);
}
}

/**
* Implements union using the buffer-by-zero trick.
* This seems to be more robust than overlay union,
* for reasons somewhat unknown.
*
* @param g0 a geometry
* @param g1 a geometry
* @return the union of the geometries
*/
private static Geometry unionBuffer(Geometry g0, Geometry g1)
{
GeometryFactory factory = g0.getFactory();
Geometry gColl = factory.createGeometryCollection(new Geometry[] { g0, g1 } );
Geometry union = gColl.buffer(0.0);
return union;
}

private boolean isBorderSegmentsSame(Geometry result, Envelope env) {
List<LineSegment> segsBefore = extractBorderSegments(g0, g1, env);

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