百度地图API 判断一个百度坐标是否在一个多边形内
本帖最后由 haozhongyang 于 2015-7-22 18:08 编辑这个是在百度地图API javascript大众版中的开源库，几何计算类GeoUtils里的一个函数。
demo如下
http://api.map.baidu.com/library/GeoUtils/1.2/examples/simple.html
我将其中“判断点是否在多边形内”调用的javascript，转写成了php。
/**
* 判断一个百度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 $point 指定点坐标
* @param $pts 多边形坐标 顺时针方向
* 传值举例
* $point['lng'] = '116.453101';
* $point['lat'] = '39.966293';
* $arr['lng'] = '116.319181';
* $arr['lat'] = '39.969369';
* $arr['lng'] = '116.453712';
* $arr['lat'] = '39.967157';
* $arr['lng'] = '116.456586';
* $arr['lat'] = '39.868433';
* $arr['lng'] = '116.326655';
* $arr['lat'] = '39.86223';
*/
function is_point_in_polygon($point, $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 = $pts;//left vertex
for ($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;
}
}
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