Koordinatenangabe mit PHP?

<?php 
$image = "grafik.gif";   
$im = imagecreatefromgif($image); 
$tc = imagecolorallocate ($im, 0, 0, 0); 


$text = "Test";   

imageString($im, 4, 10, 6, $text, $tc); 
header("Content-Type: image/gif");   
imagegif($im,'',100);   
imagedestroy ($im); 
?>