Java多边形重心计算

多边形重心计算

三角形重心

• 顶点为a，b，c的三角形重心为x = (xa + xb + xc) / 3，y = (ya + yb + yc) / 3

多边形重心

• x = (x1w1 + x2w2 + … + xnwn)/W
• y = (y1w1 + y2w2 + … + ynwn)/W

import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.Polygon;
import org.locationtech.jts.io.ParseException;
import java.util.*;
import java.util.stream.Collectors;
/**
 * <p>Title : PolygonNodeTriangle </p>
 * <p>Description : 多边形自身节点组成三角形</p>
 * @author huifer
 * @date 2018/10/15
 */
public class PolygonNodeTriangle {
  private int NUM = 3;
  private Set result_p = new HashSet();
  public static void main(String[] args) {
    //0
    double[] point1 = new double[]{0, 0};
    //1
    double[] point2 = new double[]{10, 0};
    //2
    double[] point3 = new double[]{20, 0};
    //3
    double[] point4 = new double[]{10, 10};
    List<double[]> allPoint = new ArrayList();
    allPoint.add(point1);
    allPoint.add(point3);
    allPoint.add(point4);
    PolygonNodeTriangle polygonCenterPoint = new PolygonNodeTriangle();
    // 外围
    Polygon waiwei = polygonCenterPoint.waiwei(point1, point3, point4);
    // 节点三角形
    List<Polygon> sanjiaoxing = polygonCenterPoint.triangleMothed(allPoint);
    // 外围内所有三角形
    List<Polygon> rangeTriangle = polygonCenterPoint.getRangeTriangle(waiwei, sanjiaoxing);
    // 重心xy
    double[] gravityCenterXY = polygonCenterPoint.getGravityCenterXY(rangeTriangle);
    System.out.println(rangeTriangle.size());
    System.out.println("================================================");
    double[] doubles = polygonCenterPoint. polygonGravityPoint("POLYGON((0 0, 20 0, 10 10, 0 0))");
  }
  /***
   * polygon wkt 计算重心
   * @param wkt
   * @return
   */
  private double[] polygonGravityPoint(String wkt) {

    if (!wkt.startsWith("POLYGON")) {
      return null;
    }
    Operation operation = new Operation();
    // 外围数据转 list<double[]>
    Polygon waiwei = null;
    try {
      waiwei = operation.createPolygonByWKT(wkt);
    } catch (ParseException e) {
      e.printStackTrace();
    }
    Coordinate[] coordinates = waiwei.getCoordinates();
    List<double[]> allP = new ArrayList<>();
    Arrays.stream(coordinates).forEach(
        s -> {
          double nowX = s.x;
          double nowY = s.y;
          allP.add(new double[]{nowX, nowY});
        }
    );
    List<Polygon> polygons = triangleMothed(allP);
    List<Polygon> rangeTriangle1 = getRangeTriangle(waiwei, polygons);
    double area = waiwei.getArea();
    double[] gravityCenterXY1 = getGravityCenterXY(rangeTriangle1);
    return gravityCenterXY1;
  }
  /***
   * 重心值
   * @param rangeTriangle
   * @return [x, y]
   */
  private double[] getGravityCenterXY(List<Polygon> rangeTriangle) {
    double xArea = 0.0;
    double yArea = 0.0;
    double aArea = 0.0;
    for (Polygon triangle : rangeTriangle) {
      Coordinate[] coordinates = triangle.getCoordinates();
      double area = triangle.getArea();
      double[] oneGR = triangleCenterOfGravity(coordinates[0], coordinates[1], coordinates[2]);
      xArea += oneGR[0] * area;
      yArea += oneGR[1] * area;
      aArea += area;
    }
    System.out.println("重心X " + xArea / aArea);
    System.out.println("重心Y " + yArea / aArea);
    return new double[]{xArea / aArea, yArea / aArea};
  }
  /***
   * 范围内三角形
   * @param waiwei
   * @param sanjiaoxing
   * @return
   */
  private List<Polygon> getRangeTriangle(Polygon waiwei, List<Polygon> sanjiaoxing) {
    List<Polygon> triangle = new ArrayList<>();
    // 判断三角形是否在面内
    for (int i = 0; i < sanjiaoxing.size(); i++) {
      Polygon polygon = sanjiaoxing.get(i);
      boolean within = polygon.within(waiwei);
      if (within) {
        triangle.add(polygon);
      }
    }
    return triangle;
  }
  /***
   * 三角形重心计算
   * @param a
   * @param b
   * @param c
   * @return
   */
  private double[] triangleCenterOfGravity(Coordinate a, Coordinate b, Coordinate c) {
    double gravityX = (a.x + b.x + c.x) / 3;
    double gravityY = (a.y + b.y + c.y) / 3;
    double[] result = new double[]{gravityX, gravityY};
    return result;
  }
  /***
   * 测试用外包图形
   * @return
   */
  private Polygon waiwei(double[] point1, double[] point3, double[] point4) {
    List<double[]> ceshimian = new ArrayList();
    ceshimian.add(point1);
//    ceshimian.add(point2);
//    ceshimian.add(point7);
    ceshimian.add(point4);
//    ceshimian.add(point6);
//    ceshimian.add(point5);
    ceshimian.add(point3);
    String polygonForList = createPolygonForList(ceshimian);
    Operation op = new Operation();
    Polygon polygonByWKT = null;
    try {
      polygonByWKT = op.createPolygonByWKT(polygonForList);
      return polygonByWKT;
    } catch (ParseException e) {
      e.printStackTrace();
    }
    return null;
  }
  /***
   * 生成所有三角形
   * @param allPoint
   * @return
   */
  private List<Polygon> triangleMothed(List<double[]> allPoint) {
    // 索引 -> 点坐标
    Map<String, double[]> indexOfPoint = new HashMap();
    for (int i = 0; i < allPoint.size(); i++) {
      indexOfPoint.put(String.valueOf(i), allPoint.get(i));
    }
    // 排序结果
    sort((List) indexOfPoint.keySet().stream().collect(Collectors.toList()), new HashSet());
    // 删除元素相同后的集合
    // 所有三角形
    List<Polygon> allTriangle = new ArrayList();
    for (Object oneDataObj : result_p) {
      //这一行数据
      Set oneDataList = (Set) oneDataObj;
      // 这一行数据的三角形数据
      List<double[]> trianglePoint = new ArrayList();
      oneDataList.forEach(
          s -> trianglePoint.add(indexOfPoint.get(s)
          ));
      Polygon triangle = createTriangle(trianglePoint);
      if (triangle != null) {
        allTriangle.add(triangle);
      }
    }
    // 所有三角形结束
    return allTriangle;
  }
  /***
   * 从点坐标集合中创建一个面
   * @param points
   * @return
   */
  private static String createPolygonForList(List<double[]> points) {
    String end = "))";
    String res = "POLYGON((";
    Operation op = new Operation();
    for (double[] point : points) {
      String x = Double.toString(point[0]);
      String y = Double.toString(point[1]);
      res += x + " " + y + ", ";
    }
    res += Double.toString(points.get(0)[0]) + " " + Double.toString(points.get(0)[1]);
    res += end;
    try {
      op.createPolygonByWKT(res);
    } catch (ParseException e) {
      e.printStackTrace();
    }
    return res;
  }
  /***
   * 创建三角形
   * @param trianglePoint
   * @return polygon
   */
  private static Polygon createTriangle(List<double[]> trianglePoint) {
    Operation op = new Operation();
    String triangleWkt;
    boolean isTri = isTriangle(trianglePoint);
    if (isTri) {
      triangleWkt = "POLYGON((" + trianglePoint.get(0)[0] + " " + trianglePoint.get(0)[1] + ", " + trianglePoint.get(1)[0] + " " + trianglePoint.get(1)[1] + ", " + trianglePoint.get(2)[0] + " " + trianglePoint.get(2)[1] + ", " + trianglePoint.get(0)[0] + " " + trianglePoint.get(0)[1] + "))";
      try {
        Polygon polygonByWKT = op.createPolygonByWKT(triangleWkt);
        return polygonByWKT;
//        return triangleWkt;
      } catch (ParseException e) {
        e.printStackTrace();
      }
    }
    return null;
  }
  /***
   * 判断三角形
   * @param trianglePoint
   * @return
   */
  private static boolean isTriangle(List<double[]> trianglePoint) {
    double[] doubles = trianglePoint.get(0);
    double[] doubles1 = trianglePoint.get(1);
    double[] doubles2 = trianglePoint.get(2);
    double len = Math.sqrt(Math.pow(doubles[0] - doubles1[0], 2) + Math.pow(doubles[1] - doubles1[1], 2));
    double len1 = Math.sqrt(Math.pow(doubles[0] - doubles2[0], 2) + Math.pow(doubles[1] - doubles2[1], 2));
    double len2 = Math.sqrt(Math.pow(doubles1[0] - doubles2[0], 2) + Math.pow(doubles1[1] - doubles2[1], 2));
    if ((len + len1 > len2) && (len + len2 > len1) && (len1 + len2 > len)) {
      return true;
    }
    return false;
  }
  /***
   * 不重复排列 (元素不相同)
   * @param datas
   * @param target
   */
  private void sort(List datas, Set target) {
    if (target.size() == this.NUM) {
      this.result_p.add(target);
      return;
    }
    for (int i = 0; i < datas.size(); i++) {
      List newDatas = new ArrayList(datas);
      Set newTarget = new HashSet(target);
      newTarget.add(newDatas.get(i));
      newDatas.remove(i);
      sort(newDatas, newTarget);
    }
  }
}

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