PHP determines whether a point is inside or outside the polygon area

PHP determines whether a point is inside or outside the polygon area;

According to the ray method of mathematical knowledge, if the number of points that the ray intersects with the geometric polygon is an odd number, it is inside the geometry;

An even number Externally;

/**
 * Created by PhpStorm.
 * function: inArea
 * Description: 判断点是否在多边形区域内
 * User: Xiaoxie
 * @param $x 
 * @param $y
 * @param $arr 几何订单坐标
 * @return int
 *
 */
public function inArea($x,$y,$arr)
{
    //点的数量
    $count = count($arr);
    $n = 0; //点与线相交的个数
    $bool = 0;//外
    for ($i = 0, $j = $count - 1; $i < $count; $j = $i, $i++) {
        //两个点一条线 取出两个连接点的定点
        $px1 = $arr[$i][0];
        $py1 = $arr[$i][1];
        $px2 = $arr[$j][0];
        $py2 = $arr[$j][1];
        //$x的水平位置画射线
        if($x>=$px1 || $x>= $px2)
        {
            //判断$y 是否在线的区域
            if(($y>=$py1 && $y<=$py2) || ($y>=$py2 && $y<= $py1)){
 
 
                    if (($y == $py1 && $x == $px1) || ($y == $py2 && $x == $px2)) {
 
                       #如果$x的值和点的坐标相同
                        $bool = 2;//在点上
                        return $bool;
 
                    }else{
                        $px = $px1+($y-$py1)/($py2-$py1)*($px2-$px1) ;
                        if($px ==$x)
                        {
                            $bool = 3;//在线上
                        }elseif($px< $x){
                            $n++;
                        }
 
                    }
            }
        }
 
    }
    if ($n%2 != 0) {
        $bool = 1;
    }
    return $bool;
}

Test Array

$arr = [
    ['9.4','12.04'],
    ['6.68','8.61'],
    ['9.05','6.06'],
    ['6.24','3.87'],
    ['10.02','2.55'],
 
    ['14.06','4.13'],
 
    ['16.35','7.56'],
 
    ['11.69','8.35'],
];
 
$x =15.73;
$y = 5.62;
//在外
$x = 9.97;
$y = 4.96; //在内

　

For more PHP-related knowledge, please visit PHP Tutorial!

The above is the detailed content of PHP determines whether a point is inside or outside the polygon area. For more information, please follow other related articles on the PHP Chinese website!