java判断某个点是否在所画多边形判断某个点是否在所画多边形/圆形内圆形内
主要为大家详细介绍了java判断某个点是否在所画多边形或圆形内的方法，具有一定的参考价值，感兴趣的小伙
伴们可以参考一下
本文实例为大家分享了java判断某个点是否在所画范围内的具体代码，供大家参考，具体内容如下
IsPtInPoly.java
package com.ardo.util.circle;
import java.util.ArrayList;
import java.util.List;
/**
* java判断某个点是否在所画范围内(多边形【isPtInPoly】/圆形【distencePC】)
* @param point 检测点
* @param pts 多边形的顶点
* @return 点在多边形内返回true,否则返回false
* @author ardo
*/
public class IsPtInPoly {
/**
* 判断点是否在多边形内
* @param point 检测点
* @param pts 多边形的顶点
* @return 点在多边形内返回true,否则返回false
*/
public static boolean isPtInPoly(Point2D point, List<Point2D> pts){
int N = pts.size();
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
int intersectCount = 0;//cross points count of x
double precision = 2e-10; //浮点类型计算时候与0比较时候的容差
Point2D p1, p2;//neighbour bound vertices
Point2D p = point; //当前点
p1 = pts.get(0);//left vertex
for(int i = 1; i <= N; ++i){//check all rays
if(p.equals(p1)){
return boundOrVertex;//p is an vertex
}
p2 = pts.get(i % N);//right vertex
if(p.x < Math.min(p1.x, p2.x) || p.x > Math.max(p1.x, p2.x)){//ray is outside of our interests
p1 = p2;
continue;//next ray left point
}
if(p.x > Math.min(p1.x, p2.x) && p.x < Math.max(p1.x, p2.x)){//ray is crossing over by the algorithm (common part of)
if(p.y <= Math.max(p1.y, p2.y)){//x is before of ray
if(p1.x == p2.x && p.y >= Math.min(p1.y, p2.y)){//overlies on a horizontal ray
return boundOrVertex;
}
if(p1.y == p2.y){//ray is vertical
if(p1.y == p.y){//overlies on a vertical ray
return boundOrVertex;
}else{//before ray
++intersectCount;
}
}else{//cross point on the left side
double xinters = (p.x - p1.x) * (p2.y - p1.y) / (p2.x - p1.x) + p1.y;//cross point of y
if(Math.abs(p.y - xinters) < precision){//overlies on a ray
return boundOrVertex;
}
if(p.y < xinters){//before ray
++intersectCount;
}
}
}
}else{//special case when ray is crossing through the vertex
if(p.x == p2.x && p.y <= p2.y){//p crossing over p2
Point2D p3 = pts.get((i+1) % N); //next vertex
if(p.x >= Math.min(p1.x, p3.x) && p.x <= Math.max(p1.x, p3.x)){//p.x lies between p1.x & p3.x
++intersectCount;
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