方法主体
/**
* 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.Double point, List<Point2D.Double> 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;
double precision = 2e-10; //浮点类型计算时候与0比较时候的容差
Point2D.Double p1, p2;
Point2D.Double p = point; //当前点
p1 = pts.get(0);
for(int i = 1; i <= N; ++i){
if(p.equals(p1)){
return boundOrVertex;
}
p2 = pts.get(i % N);
if(p.x < Math.min(p1.x, p2.x) || p.x > Math.max(p1.x, p2.x)){
p1 = p2;
continue;
}
if(p.x > Math.min(p1.x, p2.x) && p.x < Math.max(p1.x, p2.x)){
if(p.y <= Math.max(p1.y, p2.y)){
if(p1.x == p2.x && p.y >= Math.min(p1.y, p2.y)){
return boundOrVertex;
}
if(p1.y == p2.y){
if(p1.y == p.y){
return boundOrVertex;
}else{
++intersectCount;
}
}else{
double xinters = (p.x - p1.x) * (p2.y - p1.y) / (p2.x - p1.x) + p1.y;
if(Math.abs(p.y - xinters) < precision){
return boundOrVertex;
}
if(p.y < xinters){
++intersectCount;
}
}
}
}else{
if(p.x == p2.x && p.y <= p2.y){
Point2D.Double p3 = pts.get((i+1) % N);
if(p.x >= Math.min(p1.x, p3.x) && p.x <= Math.max(p1.x, p3.x)){
++intersectCount;
}else{
intersectCount += 2;
}
}
}
p1 = p2;
}
if(intersectCount % 2 == 0){
return false;
} else {
return true;
}
}
测试的main函数
public static void main(String[] args) {
List<Point2D.Double> list = new ArrayList<Point2D.Double>();
Point2D.Double p1 = new Point2D.Double(121.463273,31.231155);
Point2D.Double p2 = new Point2D.Double(121.463895,31.22754);
Point2D.Double p3 = new Point2D.Double(121.47177,31.231889);
Point2D.Double p4 = new Point2D.Double(121.47177,31.231889);
Point2D.Double p5 = new Point2D.Double(121.461728,31.233595);
Point2D.Double p6 = new Point2D.Double(122.461728,32.233595);
list.add(p1);
list.add(p2);
list.add(p3);
list.add(p4);
list.add(p5);
System.out.println(IsPtInPoly(p6,list));
}