package com.hxzkoa.util;
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import java.awt.geom.Point2D;
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import java.util.List;
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/**该类用于判断点是否在多边形内*/
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public class IsPtInPoly {
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/**
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* 判断点是否在多边形内
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* @param point 检测点
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* @param pts 多边形的顶点集合
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* @return 点在多边形内返回true,否则返回false
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*/
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public static boolean inPoly(Point2D.Double point, List<Point2D.Double> pts){
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int N = pts.size();
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boolean boundOrVertex = true; //如果点位于多边形的顶点或边上，也算做点在多边形内，直接返回true
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int intersectCount = 0;
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double precision = 2e-10; //浮点类型计算时候与0比较时候的容差
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Point2D.Double p1, p2;
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Point2D.Double p = point; //当前点
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p1 = pts.get(0);
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for(int i = 1; i <= N; ++i){
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if(p.equals(p1)){
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return boundOrVertex;
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}
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p2 = pts.get(i % N);
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if(p.x < Math.min(p1.x, p2.x) || p.x > Math.max(p1.x, p2.x)){
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p1 = p2;
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continue;
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}
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if(p.x > Math.min(p1.x, p2.x) && p.x < Math.max(p1.x, p2.x)){
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if(p.y <= Math.max(p1.y, p2.y)){
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if(p1.x == p2.x && p.y >= Math.min(p1.y, p2.y)){
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return boundOrVertex;
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}
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if(p1.y == p2.y){
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if(p1.y == p.y){
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return boundOrVertex;
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}else{
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++intersectCount;
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}
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}else{
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double xinters = (p.x - p1.x) * (p2.y - p1.y) / (p2.x - p1.x) + p1.y;
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if(Math.abs(p.y - xinters) < precision){
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return boundOrVertex;
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}
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if(p.y < xinters){
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++intersectCount;
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}
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}
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}
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}else{
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if(p.x == p2.x && p.y <= p2.y){
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Point2D.Double p3 = pts.get((i+1) % N);
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if(p.x >= Math.min(p1.x, p3.x) && p.x <= Math.max(p1.x, p3.x)){
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++intersectCount;
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}else{
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intersectCount += 2;
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}
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}
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}
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p1 = p2;
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}
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if(intersectCount % 2 == 0){
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return false;
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} else {
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return true;
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}
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}
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}
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