include/geos/algorithm/MinimumDiameter.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_MINIMUMDIAMETER_H
  17 #define GEOS_ALGORITHM_MINIMUMDIAMETER_H
  18
  19 #include <geos/export.h>
  20
  21 // Forward declarations
  22 namespace geos {
  23         namespace geom {
  24                 class Geometry;
  25                 class LineSegment;
  26                 class LineString;
  27                 class Coordinate;
  28                 class CoordinateSequence;
  29         }
  30 }
  31
  32
  33 namespace geos {
  34 namespace algorithm { // geos::algorithm
  35
  36 /** \brief
  37  * Computes the minimum diameter of a geom::Geometry
  38  *
  39  * The minimum diameter is defined to be the
  40  * width of the smallest band that
  41  * contains the geometry,
  42  * where a band is a strip of the plane defined
  43  * by two parallel lines.
  44  * This can be thought of as the smallest hole that the geometry can be
  45  * moved through, with a single rotation.
  46  * <p>
  47  * The first step in the algorithm is computing the convex hull of the Geometry.
  48  * If the input Geometry is known to be convex, a hint can be supplied to
  49  * avoid this computation.
  50  *
  51  * @see ConvexHull
  52  *
  53  */
  54 class GEOS_DLL MinimumDiameter {
  55 private:
  56         const geom::Geometry* inputGeom;
  57         bool isConvex;
  58         geom::LineSegment* minBaseSeg;
  59         geom::Coordinate* minWidthPt;
  60         int minPtIndex;
  61         double minWidth;
  62         void computeMinimumDiameter();
  63         void computeWidthConvex(const geom::Geometry* geom);
  64
  65         /**
  66          * Compute the width information for a ring of {@link geom::Coordinate}s.
  67          * Leaves the width information in the instance variables.
  68          *
  69          * @param pts
  70          * @return
  71          */
  72         void computeConvexRingMinDiameter(const geom::CoordinateSequence *pts);
  73
  74         unsigned int findMaxPerpDistance(const geom::CoordinateSequence* pts,
  75                 geom::LineSegment* seg, unsigned int startIndex);
  76
  77         static unsigned int getNextIndex(const geom::CoordinateSequence* pts,
  78                 unsigned int index);
  79
  80 public:
  81         ~MinimumDiameter();
  82
  83         /** \brief
  84          * Compute a minimum diameter for a giver {@link Geometry}.
  85          *
  86          * @param geom a Geometry
  87          */
  88         MinimumDiameter(const geom::Geometry* newInputGeom);
  89
  90         /** \brief
  91          * Compute a minimum diameter for a given Geometry,
  92          * with a hint if the Geometry is convex
  93          * (e.g. a convex Polygon or LinearRing,
  94          * or a two-point LineString, or a Point).
  95          *
  96          * @param geom a Geometry which is convex
  97          * @param isConvex <code>true</code> if the input geometry is convex
  98          */
  99         MinimumDiameter(const geom::Geometry* newInputGeom,
 100                         const bool newIsConvex);
 101
 102         /** \brief
 103          * Gets the length of the minimum diameter of the input Geometry
 104          *
 105          * @return the length of the minimum diameter
 106          */
 107         double getLength();
 108
 109         /** \brief
 110          * Gets the {@link geom::Coordinate} forming one end of the minimum diameter
 111          *
 112          * @return a coordinate forming one end of the minimum diameter
 113          */
 114         geom::Coordinate* getWidthCoordinate();
 115
 116         /** \brief
 117          * Gets the segment forming the base of the minimum diameter
 118          *
 119          * @return the segment forming the base of the minimum diameter
 120          */
 121         geom::LineString* getSupportingSegment();
 122
 123         /** \brief
 124          * Gets a LineString which is a minimum diameter
 125          *
 126          * @return a LineString which is a minimum diameter
 127          */
 128         geom::LineString* getDiameter();
 129 };
 130
 131 } // namespace geos::algorithm
 132 } // namespace geos
 133
 134 #endif // GEOS_ALGORITHM_MINIMUMDIAMETER_H
 135
 136 /**********************************************************************
 137  * $Log$
 138  * Revision 1.1  2006/03/09 16:46:48  strk
 139  * geos::geom namespace definition, first pass at headers split
 140  *
 141  **********************************************************************/
 142