[PHP] GD installed but imageFUNCTIONS dont work

[Helmut Ott]

Hi, 
hopefully somebody can help to solve this miracle.

My phpinfo

My provider (and phpinfo) says GD <=1.62 is installed.
But when I run scripts using the php-imagefunctions 
that require gd like 
<?php
Header ("Content-type: image/jpeg");
$im = imagecreate (400, 30);
$black = ImageColorAllocate ($im, 0, 0, 0);
$white = ImageColorAllocate ($im, 255, 255, 255);
ImageTTFText ($im, 20, 0, 10, 20, $white, "/path/arial.ttf", 
              "Testing... Omega: &#937;");
ImageJPEG ($im);
ImageDestroy ($im);
?>
The lines containing the functions like createImage(), or ImagecolorAllocate() return 
error messages.
How can I find out without doubt whether the functions work properly or not?
Every advice is appreciated.

Helmut