include/geos/algorithm/InteriorPointArea.h

   1 /**********************************************************************
   2  *
   3  * GEOS - Geometry Engine Open Source
   4  * http://geos.osgeo.org
   5  *
   6  * Copyright (C) 2005-2006 Refractions Research Inc.
   7  * Copyright (C) 2001-2002 Vivid Solutions Inc.
   8  *
   9  * This is free software; you can redistribute and/or modify it under
  10  * the terms of the GNU Lesser General Public Licence as published
  11  * by the Free Software Foundation.
  12  * See the COPYING file for more information.
  13  *
  14  **********************************************************************/
  15
  16 #ifndef GEOS_ALGORITHM_INTERIORPOINTAREA_H
  17 #define GEOS_ALGORITHM_INTERIORPOINTAREA_H
  18
  19 #include <geos/export.h>
  20 #include <geos/geom/Coordinate.h>
  21
  22 // Forward declarations
  23 namespace geos {
  24         namespace geom {
  25                 class Geometry;
  26                 class LineString;
  27                 class GeometryFactory;
  28                 class GeometryCollection;
  29         }
  30 }
  31
  32
  33 namespace geos {
  34 namespace algorithm { // geos::algorithm
  35
  36 /** \brief
  37  * Computes a point in the interior of an area geometry.
  38  *
  39  * <h2>Algorithm</h2>
  40  * <ul>
  41  *   <li>Find the intersections between the geometry
  42  *       and the horizontal bisector of the area's envelope
  43  *   <li>Pick the midpoint of the largest intersection (the intersections
  44  *       will be lines and points)
  45  * </ul>
  46  *
  47  * <b>
  48  * Note: If a fixed precision model is used,
  49  * in some cases this method may return a point
  50  * which does not lie in the interior.
  51  * </b>
  52  */
  53 class GEOS_DLL InteriorPointArea {
  54
  55 private:
  56
  57         bool foundInterior;
  58
  59         const geom::GeometryFactory *factory;
  60
  61         geom::Coordinate interiorPoint;
  62
  63         double maxWidth;
  64
  65         void add(const geom::Geometry *geom);
  66
  67         const geom::Geometry *widestGeometry(const geom::Geometry *geometry);
  68
  69         const geom::Geometry *widestGeometry(const geom::GeometryCollection *gc);
  70
  71         geom::LineString *horizontalBisector(const geom::Geometry *geometry);
  72
  73 public:
  74
  75         InteriorPointArea(const geom::Geometry *g);
  76
  77         ~InteriorPointArea();
  78
  79         bool getInteriorPoint(geom::Coordinate& ret) const;
  80
  81         /** \brief
  82          * Finds a reasonable point at which to label a Geometry.
  83          *
  84          * @param geometry the geometry to analyze
  85          * @return the midpoint of the largest intersection between the geometry and
  86          * a line halfway down its envelope
  87          */
  88         void addPolygon(const geom::Geometry *geometry);
  89
  90 };
  91
  92 } // namespace geos::algorithm
  93 } // namespace geos
  94
  95 #endif // GEOS_ALGORITHM_INTERIORPOINTAREA_H
  96
  97 /**********************************************************************
  98  * $Log$
  99  * Revision 1.1  2006/03/09 16:46:48  strk
 100  * geos::geom namespace definition, first pass at headers split
 101  *
 102  **********************************************************************/
 103