Java多边形重心计算

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;

/**

*

Title : PolygonNodeTriangle

*

Description : 多边形自身节点组成三角形

* @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 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 sanjiaoxing = polygonCenterPoint.triangleMothed(allPoint);

// 外围内所有三角形

List 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

Polygon waiwei = null;

try {

waiwei = operation.createPolygonByWKT(wkt);

} catch (ParseException e) {

e.printStackTrace();

}

Coordinate[] coordinates = waiwei.getCoordinates();

List allP = new ArrayList<>();

Arrays.stream(coordinates).forEach(

s -> {

double nowX = s.x;

double nowY = s.y;

allP.add(new double[]{nowX, nowY});

}

);

List polygons = triangleMothed(allP);

List 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 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 getRangeTriangle(Polygon waiwei, List sanjiaoxing) {

List 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 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 triangleMothed(List allPoint) {

// 索引 -> 点坐标

Map 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 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 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 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 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 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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