java判断某个点是否在所画多边形/圆形内

发布日期： 2026-01-12 阅读量： 作者： 用户投稿

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; 
  } 
   
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。

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