判断一个点是否在矩形内部

以你之姓@ 2022-05-28 06:23 203阅读 0赞

![20180330221327550][]

//判断一个点是否在矩形内部
    public class InMatrix{
    	
         //(1)特殊情况，矩形平行于x轴和y轴
         public static boolean isInMatrix(double x1,double y1,double x4,double y4,double x,double y){
            
            if(x<=x1)
            {
            	 return false;
            }
            if(x>=x4)
            {
            	 return false;
            }
            if(y>=y1)
            {
            	 return false;
            }
            if(y<=y4)
            {
            	 return false;
            }
    
         	return true;
         }
    
         //(2)一般情况，求一个点是否在一个矩阵中(转换成平行成x,y轴)
         public static boolean isInSide(double x1,double y1,double x2,double y2,
         	                            double x3,double y3,double x4,double y4,double x,double y)
         {
            
             if(y1==y2)
             {
             	 return isInMatrix(x1,y1,x4,y4,x,y);
             }
         	 double l=Math.abs(y4-y3);
         	 double k=Math.abs(x4-x3);
         	 double s=Math.sqrt(k*k+l*l); //第三边的长度
         	 double sin=l/s;
         	 double cos=k/s;
         	 double x1R=cos*x1+sin*y1;
         	 double y1R=-x1*sin+y1*cos;
         	 double x4R=cos*x4+sin*x4;
         	 double y4R=-x4*sin+y4*cos;
         	 double xR=cos*x+sin*y;
         	 double yR=-x*sin+y*cos;
    
         	return isInMatrix(x1R,y1R,x4R,y4R,xR,yR);
         }
    
    	 public static void main(String[]args)
    	 {
    	     //System.out.println("Hello");
    	 	double x1 = 0;
    		double y1 = 3;// (x1,y1) should be the most left
    		double x2 = 3;
    		double y2 = 7;// (x2,y2) should be the most top.
    		double x3 = 4;
    		double y3 = 0;// (x3,y3) should be the most below.
    		double x4 = 7;
    		double y4 = 4;// (x4,y4) should be the most right.
    
    		double x = 4;
    		double y = 3;
    		System.out.print(isInSide(x1, y1, x2, y2, x3, y3, x4, y4, x, y));
    	 }
    }

[20180330221327550]: /images/20220528/b5d103432a7743a0af80b2777d75c6dc.png