判断点在多边形区域内外
<ul>
<li>根据数学知识的射线法，射线与几何多边形相交的点的个数为奇数则是在几何内部；</li>
</ul>
<h2>实现</h2>
<pre><code class="language-php">function inArea($x, $y, array $arr)
{
$bool = 0;//外
if (empty($arr)) {
return $bool;
}
//点的数量
$count = count($arr);
$n = 0;//点与线相交的个数
for ($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 $bool;
}</code></pre>
<h2>测试数据</h2>
<pre><code class="language-php">$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'],
];</code></pre>
<h2>测试-在多边形区域外</h2>
<pre><code class="language-php">$x = 15.73;
$y = 5.62;
$result = inArea($x, $y, $arr);
print_r($result); // 0</code></pre>
<h2>测试-在多边形区域内</h2>
<pre><code class="language-php">$x = 9.97;
$y = 4.96;
$result = inArea($x, $y, $arr);
print_r($result); // 1</code></pre>