[FEATURE] Expose GEOS Voronoi and delaunay triangulation to QgsGeometry

python/core/geometry/qgsgeometry.sip

@@ -567,6 +567,10 @@ class QgsGeometry
     /** Returns the smallest convex polygon that contains all the points in the geometry. */
     QgsGeometry convexHull() const;
 
+    QgsGeometry voronoiDiagram( const QgsGeometry& extent = QgsGeometry(), double tolerance = 0.0, bool edgesOnly = false ) const;
+
+    QgsGeometry delaunayTriangulation( double tolerance = 0.0, bool edgesOnly = false ) const;
+
     /**
      * Return interpolated point on line at distance
      * @note added in 1.9

src/core/geometry/qgsgeometry.cpp

@@ -1606,6 +1606,28 @@ QgsGeometry QgsGeometry::convexHull() const
   return QgsGeometry( cHull );
 }
 
+QgsGeometry QgsGeometry::voronoiDiagram( const QgsGeometry& extent, double tolerance, bool edgesOnly ) const
+{
+  if ( !d->geometry )
+  {
+    return QgsGeometry();
+  }
+
+  QgsGeos geos( d->geometry );
+  return geos.voronoiDiagram( extent.geometry(), tolerance, edgesOnly );
+}
+
+QgsGeometry QgsGeometry::delaunayTriangulation( double tolerance, bool edgesOnly ) const
+{
+  if ( !d->geometry )
+  {
+    return QgsGeometry();
+  }
+
+  QgsGeos geos( d->geometry );
+  return geos.delaunayTriangulation( tolerance, edgesOnly );
+}
+
 QgsGeometry QgsGeometry::interpolate( double distance ) const
 {
   if ( !d->geometry )

src/core/geometry/qgsgeometry.h

@@ -633,6 +633,34 @@ class CORE_EXPORT QgsGeometry
     //! Returns the smallest convex polygon that contains all the points in the geometry.
     QgsGeometry convexHull() const;
 
+    /**
+     * Creates a Voronoi diagram for the nodes contained within the geometry.
+     *
+     * Returns the Voronoi polygons for the nodes contained within the geometry.
+     * If \a extent is specified then it will be used as a clipping envelope for the diagram.
+     * If no extent is set then the clipping envelope will be automatically calculated.
+     * In either case the diagram will be clipped to the larger of the provided envelope
+     * OR the envelope surrounding all input nodes.
+     * The \a tolerance parameter specifies an optional snapping tolerance which can
+     * be used to improve the robustness of the diagram calculation.
+     * If \a edgesOnly is true than line string boundary geometries will be returned
+     * instead of polygons.
+     * An empty geometry will be returned if the diagram could not be calculated.
+     * @note added in QGIS 3.0
+     */
+    QgsGeometry voronoiDiagram( const QgsGeometry& extent = QgsGeometry(), double tolerance = 0.0, bool edgesOnly = false ) const;
+
+    /**
+     * Returns the Delaunay triangulation for the vertices of the geometry.
+     * The \a tolerance parameter specifies an optional snapping tolerance which can
+     * be used to improve the robustness of the triangulation.
+     * If \a edgesOnly is true than line string boundary geometries will be returned
+     * instead of polygons.
+     * An empty geometry will be returned if the diagram could not be calculated.
+     * @note added in QGIS 3.0
+     */
+    QgsGeometry delaunayTriangulation( double tolerance = 0.0, bool edgesOnly = false ) const;
+
     /**
      * Return interpolated point on line at distance
      * @note added in 1.9

src/core/geometry/qgsgeos.cpp

@@ -1980,6 +1980,62 @@ QgsGeometry QgsGeos::polygonize( const QList<QgsAbstractGeometry*>& geometries,
   }
 }
 
+QgsGeometry QgsGeos::voronoiDiagram( const QgsAbstractGeometry* extent, double tolerance, bool edgesOnly, QString* errorMsg ) const
+{
+  if ( !mGeos )
+  {
+    return QgsGeometry();
+  }
+
+  GEOSGeometry* extentGeos = nullptr;
+  GEOSGeomScopedPtr extentGeosGeom( nullptr );
+  if ( extent )
+  {
+    extentGeosGeom.reset( asGeos( extent, mPrecision ) );
+    if ( !extentGeosGeom )
+    {
+      return QgsGeometry();
+    }
+    extentGeos = extentGeosGeom.get();
+  }
+
+  GEOSGeomScopedPtr geos;
+  try
+  {
+    geos.reset( GEOSVoronoiDiagram_r( geosinit.ctxt, mGeos, extentGeos, tolerance, edgesOnly ) );
+
+    if ( !geos || GEOSisEmpty_r( geosinit.ctxt, geos.get() ) != 0 )
+    {
+      return QgsGeometry();
+    }
+
+    return QgsGeometry( fromGeos( geos.get() ) );
+  }
+  CATCH_GEOS_WITH_ERRMSG( QgsGeometry() );
+}
+
+QgsGeometry QgsGeos::delaunayTriangulation( double tolerance, bool edgesOnly, QString* errorMsg ) const
+{
+  if ( !mGeos )
+  {
+    return QgsGeometry();
+  }
+
+  GEOSGeomScopedPtr geos;
+  try
+  {
+    geos.reset( GEOSDelaunayTriangulation_r( geosinit.ctxt, mGeos, tolerance, edgesOnly ) );
+
+    if ( !geos || GEOSisEmpty_r( geosinit.ctxt, geos.get() ) != 0 )
+    {
+      return QgsGeometry();
+    }
+
+    return QgsGeometry( fromGeos( geos.get() ) );
+  }
+  CATCH_GEOS_WITH_ERRMSG( QgsGeometry() );
+}
+
 
 //! Extract coordinates of linestring's endpoints. Returns false on error.
 static bool _linestringEndpoints( const GEOSGeometry* linestring, double& x1, double& y1, double& x2, double& y2 )

src/core/geometry/qgsgeos.h

@@ -152,6 +152,34 @@ class CORE_EXPORT QgsGeos: public QgsGeometryEngine
      */
     static QgsGeometry polygonize( const QList<QgsAbstractGeometry*>& geometries, QString* errorMsg = nullptr );
 
+    /**
+     * Creates a Voronoi diagram for the nodes contained within the geometry.
+     *
+     * Returns the Voronoi polygons for the nodes contained within the geometry.
+     * If \a extent is specified then it will be used as a clipping envelope for the diagram.
+     * If no extent is set then the clipping envelope will be automatically calculated.
+     * In either case the diagram will be clipped to the larger of the provided envelope
+     * OR the envelope surrounding all input nodes.
+     * The \a tolerance parameter specifies an optional snapping tolerance which can
+     * be used to improve the robustness of the diagram calculation.
+     * If \a edgesOnly is true than line string boundary geometries will be returned
+     * instead of polygons.
+     * An empty geometry will be returned if the diagram could not be calculated.
+     * @note added in QGIS 3.0
+     */
+    QgsGeometry voronoiDiagram( const QgsAbstractGeometry* extent = nullptr, double tolerance = 0.0, bool edgesOnly = false, QString* errorMsg = nullptr ) const;
+
+    /**
+     * Returns the Delaunay triangulation for the vertices of the geometry.
+     * The \a tolerance parameter specifies an optional snapping tolerance which can
+     * be used to improve the robustness of the triangulation.
+     * If \a edgesOnly is true than line string boundary geometries will be returned
+     * instead of polygons.
+     * An empty geometry will be returned if the diagram could not be calculated.
+     * @note added in QGIS 3.0
+     */
+    QgsGeometry delaunayTriangulation( double tolerance = 0.0, bool edgesOnly = false, QString* errorMsg = nullptr ) const;
+
     /** Create a geometry from a GEOSGeometry
      * @param geos GEOSGeometry. Ownership is NOT transferred.
      */