舒孝元博客

# 废话少说，直接上代码

- 这个是我用的一个精准度很高的算法，文末给出了其他算法链接，可以参考

```
<?php

namespace App\Http\Controllers;

class GeoUtilsController extends Controller {
	
	/**
	 * 判断一个坐标是否在一个多边形内（由多个坐标围成的）
	 * 基本思想是利用射线法，计算射线与多边形各边的交点，如果是偶数，则点在多边形外，否则
	 * 在多边形内。还会考虑一些特殊情况，如点在多边形顶点上，点在多边形边上等特殊情况。
	 * @param array $point 指定点坐标,一维数组 ['lng'=>121.427417,'lat'=>31.20357];
	 * @param array $pts 多边形坐标，二维数组，顺时针方向 [['lng'=>121.23036,'lat'=>31.218609],['lng'=>121.233666,'lat'=>31.210579],['lng'=>121.247177,'lat'=>31.206749],['lng'=>121.276353,'lat'=>31.190811],['lng'=>121.267442,'lat'=>31.237383],];
	 * @return bool
	 */
	public function is_point_in_polygon( array $point, array $pts) {
		$N = count($pts);
		$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
		$intersectCount = 0;//cross points count of x
		$precision = 2e-10; //浮点类型计算时候与0比较时候的容差
		$p1 = 0;//neighbour bound vertices
		$p2 = 0;
		$p = $point; //测试点
		
		$p1 = $pts[0];//left vertex
		for ($i = 1; $i <= $N; ++$i) {//check all rays
			// dump($p1);
			if ($p['lng'] == $p1['lng'] && $p['lat'] == $p1['lat']) {
				return $boundOrVertex;//p is an vertex
			}
			
			$p2 = $pts[$i % $N];//right vertex
			if ($p['lat'] < min($p1['lat'], $p2['lat']) || $p['lat'] > max($p1['lat'], $p2['lat'])) {//ray is outside of our interests
				$p1 = $p2;
				continue;//next ray left point
			}
			
			if ($p['lat'] > min($p1['lat'], $p2['lat']) && $p['lat'] < max($p1['lat'], $p2['lat'])) {//ray is crossing over by the algorithm (common part of)
				if ($p['lng'] <= max($p1['lng'], $p2['lng'])) {//x is before of ray
					if ($p1['lat'] == $p2['lat'] && $p['lng'] >= min($p1['lng'], $p2['lng'])) {//overlies on a horizontal ray
						return $boundOrVertex;
					}
					
					if ($p1['lng'] == $p2['lng']) {//ray is vertical
						if ($p1['lng'] == $p['lng']) {//overlies on a vertical ray
							return $boundOrVertex;
						} else {//before ray
							++$intersectCount;
						}
					} else {//cross point on the left side
						$xinters = ($p['lat'] - $p1['lat']) * ($p2['lng'] - $p1['lng']) / ($p2['lat'] - $p1['lat']) + $p1['lng'];//cross point of lng
						if (abs($p['lng'] - $xinters) < $precision) {//overlies on a ray
							return $boundOrVertex;
						}
						
						if ($p['lng'] < $xinters) {//before ray
							++$intersectCount;
						}
					}
				}
			} else {//special case when ray is crossing through the vertex
				if ($p['lat'] == $p2['lat'] && $p['lng'] <= $p2['lng']) {//p crossing over p2
					$p3 = $pts[($i + 1) % $N]; //next vertex
					if ($p['lat'] >= min($p1['lat'], $p3['lat']) && $p['lat'] <= max($p1['lat'], $p3['lat'])) { //p.lat lies between p1.lat & p3.lat
						++$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;
		}
	}
}

```

> 注：参考链接
- 参考文章：https://www.cnblogs.com/dcb3688/p/4608026.html
- 百度算法示例：http://api.map.baidu.com/library/GeoUtils/1.2/examples/simple.html

PHP判断点是否在多边形内