Server-side checking of a point's existence inside a polygonal area using Google Maps API v3

问题

The logic is: user is editing an existing polygonal area of which extreme points are stored in the database. After editing the modified co-ordinates are updated in the database. Now I need to find whether a certain point exists inside the modified polygon or not. For that I'm assuming I have to do the server-side checking. The client-side checking is easily done by javaScript and that I've done already. The real problem I'm having is to check this on the server-side. Any suggestions?

回答1:

I have implemented server side point in polygon in PHP.

<?php
//Point-In-Polygon Algorithm test parameters
$polySides  = 4; //how many corners the polygon has
$polyX    =  array(4,9,11,2);//horizontal coordinates of corners
$polyY    =  array(10,7,2,2);//vertical coordinates of corners
$x = 3.5;//point
//$y = 13.5;//Outside
$y = 3.5;//Inside

function pointInPolygon($polySides,$polyX,$polyY,$x,$y) {
  $j = $polySides-1 ;
  $oddNodes = 0;
  for ($i=0; $i<$polySides; $i++) {
    if ($polyY[$i]<$y && $polyY[$j]>=$y 
 ||  $polyY[$j]<$y && $polyY[$i]>=$y) {
    if ($polyX[$i]+($y-$polyY[$i])/($polyY[$j]-$polyY[$i])*($polyX[$j]-$polyX[$i])<$x)    {
    $oddNodes=!$oddNodes; }}
   $j=$i; }

  return $oddNodes; }

//Test 
 if (pointInPolygon($polySides,$polyX,$polyY,$x,$y)){
  echo "Is in polygon!";
}
else echo "Is not in polygon";
?>

This can be modified to suit language of choice ie. C#

来源：https://stackoverflow.com/questions/14394719/server-side-checking-of-a-points-existence-inside-a-polygonal-area-using-google