Package org.locationtech.jts.algorithm

Class Centroid

java.lang.Object
org.locationtech.jts.algorithm.Centroid
public class Centroid extends Object
Computes the centroid of a Geometry of any dimension. If the geometry is nominally of higher dimension, but has lower effective dimension (i.e. contains only components having zero length or area), the centroid will be computed as for the equivalent lower-dimension geometry. If the input geometry is empty, a null Coordinate is returned.

Algorithm

  • Dimension 2 - the centroid is computed as the weighted sum of the centroids of a decomposition of the area into (possibly overlapping) triangles. Holes and multipolygons are handled correctly. See http://www.faqs.org/faqs/graphics/algorithms-faq/ for further details of the basic approach.
  • Dimension 1 - Computes the average of the midpoints of all line segments weighted by the segment length. Zero-length lines are treated as points.
  • Dimension 0 - Compute the average coordinate for all points. Repeated points are all included in the average.
Version:
1.7

  • Field Details

    • areaBasePt

      private Coordinate areaBasePt

    • triangleCent3

      private Coordinate triangleCent3

    • areasum2

      private double areasum2

    • cg3

      private Coordinate cg3

    • lineCentSum

      private Coordinate lineCentSum

    • totalLength

      private double totalLength

    • ptCount

      private int ptCount

    • ptCentSum

      private Coordinate ptCentSum

  • Constructor Details

    • Centroid

      public Centroid(Geometry geom)
      Creates a new instance for computing the centroid of a geometry

  • Method Details

    • getCentroid

      public static Coordinate getCentroid(Geometry geom)
      Computes the centroid point of a geometry.
      Parameters:
      geom - the geometry to use
      Returns:
      the centroid point, or null if the geometry is empty

    • add

      private void add(Geometry geom)
      Adds a Geometry to the centroid total.
      Parameters:
      geom - the geometry to add

    • getCentroid

      public Coordinate getCentroid()
      Gets the computed centroid.
      Returns:
      the computed centroid, or null if the input is empty

    • setAreaBasePoint

      private void setAreaBasePoint(Coordinate basePt)

    • add

      private void add(Polygon poly)

    • addShell

      private void addShell(Coordinate[] pts)

    • addHole

      private void addHole(Coordinate[] pts)

    • addTriangle

      private void addTriangle(Coordinate p0, Coordinate p1, Coordinate p2, boolean isPositiveArea)

    • centroid3

      private static void centroid3(Coordinate p1, Coordinate p2, Coordinate p3, Coordinate c)
      Computes three times the centroid of the triangle p1-p2-p3. The factor of 3 is left in to permit division to be avoided until later.

    • area2

      private static double area2(Coordinate p1, Coordinate p2, Coordinate p3)
      Returns twice the signed area of the triangle p1-p2-p3. The area is positive if the triangle is oriented CCW, and negative if CW.

    • addLineSegments

      private void addLineSegments(Coordinate[] pts)
      Adds the line segments defined by an array of coordinates to the linear centroid accumulators.
      Parameters:
      pts - an array of Coordinates

    • addPoint

      private void addPoint(Coordinate pt)
      Adds a point to the point centroid accumulator.
      Parameters:
      pt - a Coordinate