<pre class="brush:php;">    function resize_image($filename, $tmpname, $xmax, $ymax)
{
    $ext = explode(".", $filename);
    $ext = $ext[count($ext)-1];  

    if($ext == "jpg" || $ext == "jpeg")
        $im = imagecreatefromjpeg($tmpname);
    elseif($ext == "png")
        $im = imagecreatefrompng($tmpname);
    elseif($ext == "gif")
        $im = imagecreatefromgif($tmpname);  

    $x = imagesx($im);
    $y = imagesy($im);  

    if($x ＜= $xmax &amp;&amp; $y ＜= $ymax)
        return $im;  

    if($x ＞= $y) {
        $newx = $xmax;
        $newy = $newx * $y / $x;
    }
    else {
        $newy = $ymax;
        $newx = $x / $y * $newy;
    }  

    $im2 = imagecreatetruecolor($newx, $newy);
    imagecopyresized($im2, $im, 0, 0, 0, 0, floor($newx), floor($newy), $x, $y);
    return $im2;
}
```