Java多边形重心计算

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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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原文链接：https://blog.csdn.net/staHuri/article/details/83058930