"Could not find/open font" when using PHP gd

I am getting this error Could not find/open fo开发者_开发技巧nt When trying imagettftext() in PHP.

The font file is there. What is the problem?

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I found the answer on bytes http://bytes.com/topic/php/answers/4833-gd-could-not-find-open-font-font-problem

Setting the gdfontpath may help

$fontpath = realpath('.'); //replace . with a different directory if needed
putenv('GDFONTPATH='.$fontpath);
$font = 't.otf';
...
$box = imagettfbbox($size, 0, $font, $text);