Image CROP functie

$streepje = "-";
$extentie = ".jpg";
$cijfer1 = mt_rand(1, 9);

$newfilename = $Datum . $streepje . $cijfer1 . $extentie;

$change="";
$abc="";

define ("MAX_SIZE","450");
function getExtension($str) {
         $i = strrpos($str,".");
         if (!$i) { return ""; }
         $l = strlen($str) - $i;
         $ext = substr($str,$i+1,$l);
         return $ext;
 }

$errors=0;
  
if($_SERVER["REQUEST_METHOD"] == "POST")
   {
      $image = $_FILES['bestand']['name'];
      $uploadedfile = $_FILES['bestand']['tmp_name'];
     
if ($image) 
   {
      $filename = stripslashes($_FILES['bestand']['name']);
      $extension = getExtension($filename);
      $extension = strtolower($extension);
		
if (($extension != "jpg") && ($extension != "jpeg")) 
   {
      $change='<div class="msgdiv">Gebruik ENKEL *.jpg of *.jpeg bestanden!</div> ';
      $errors=1;
   }
   else
   {

$uploadedfile = $_FILES['bestand']['tmp_name'];
$src = imagecreatefromjpeg($uploadedfile);

list($width,$height)=getimagesize($uploadedfile);

$newwidth=450;
$newheight=450;
//$newheight=($height/$width)*$newwidth;
$tmp=imagecreatetruecolor($newwidth,$newheight);

imagecopyresampled($tmp,$src,0,0,0,0,$newwidth,$newheight,$width,$height);

$filename = $_SERVER['DOCUMENT_ROOT'] . "/img_artiesten/". $_FILES['bestand']['name'];

imagejpeg($tmp,$filename,100);

imagedestroy($tmp);
imagedestroy($src);

}
}
}

rename("$filename", $_SERVER['DOCUMENT_ROOT'] . "/img_artiesten/$newfilename");