java判断某个点是否在所画多边形/圆形内

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;
          }else{
            intersectCount += 2;
          }
        }
      }
      p1 = p2;//next ray left point
    }  

    if(intersectCount % 2 == 0){//偶数在多边形外
      return false;
    } else { //奇数在多边形内
      return true;
    }  

  }  

  /**
   * 判断是否在圆形内
   * @param p
   * @param c
   * @return
   */
  public static String distencePC(Point2D p,Circle c){//判断点与圆心之间的距离和圆半径的关系
    String s ;
    double d2 = Math.hypot( (p.getX() - c.getCC().getX() ), (p.getY() - c.getCC().getY()) );
    System.out.println("d2=="+d2);
    double r = c.getR();
    if(d2 > r){
       s = "圆外";
    }else if(d2 < r){
       s = "圆内";
    }else{
       s = "圆上";
    }
    return s;
  }  

  public static void main(String[] args) {  

    Point2D point = new Point2D(116.404072, 39.916605);  

    // 测试一个点是否在多边形内
    List<Point2D> pts = new ArrayList<Point2D>();
    pts.add(new Point2D(116.395, 39.910));
    pts.add(new Point2D(116.394, 39.914));
    pts.add(new Point2D(116.403, 39.920));
    pts.add(new Point2D(116.402, 39.914));
    pts.add(new Point2D(116.410, 39.913));  

    if(isPtInPoly(point, pts)){
      System.out.println("点在多边形内");
    }else{
      System.out.println("点在多边形外");
    }  

    // 测试一个点是否在圆形内
    Point2D centerPoint = new Point2D(116.404172, 39.916605);
    Circle c = new Circle();
    c.setCC(centerPoint);
    c.setR(0.0056);
    String s = distencePC(point,c);
    System.out.println("点是否在圆内："+s);
  }  

} 

Circle.java

/**
 * 圆形类
 * @author ardo
 *
 */
public class Circle {
   private double r;
   private Point2D cc; 

   public void setR(double a){
      r = a;
   }
   public void setCC(Point2D centerOfCir){
      cc = centerOfCir;
   }
   public double getR(){
      return r;
   }
   public Point2D getCC(){
      return cc;
   }
} 

Point2D.java

public class Point2D { 

  public double x;
  public double y; 

  public Point2D(double x, double y) {
    super();
    this.x = x;
    this.y = y;
  } 

  public double getX() {
    return x;
  }
  public void setX(double x) {
    this.x = x;
  }
  public double getY() {
    return y;
  }
  public void setY(double y) {
    this.y = y;
  } 

} 

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