problem s imagecolorallocate()

http://agae.sk/new/

<?php
header('Content-Type: image/png');
$im = imagecreatefrompng('1.png');
$text = 'Zľavy';
$font = 'arial.ttf';
$cerna = imagecolorallocate($im, 0, 0, 0); // chcam mat text ciernej farby
imagettftext($im, 7, 10, 20, 20, $cerna, $font, $text);
imagepng($im);
imagedestroy($im);
?>

<?php
header('Content-Type: image/png');
$im = imagecreatefrompng('1.png');
$text = 'Zľavy';
$font = 'arial.ttf';
$cerna = imagecolorallocate($im, 0, 0, 0); //definovanie hociakej farby
imagecolordeallocate($im, $cerna); //undefinovanie farby :D
$cerna = imagecolorallocate($im, 0, 0, 0); // a znova defiovanie :D
imagettftext($im, 7, 10, 20, 20, $cerna, $font, $text);
imagepng($im);
imagedestroy($im);
?>