please, replace ImageString to ImageTTFString

[zvn]

ImageString is using with one byte per character encodings

[Aly]

You mean?

imagettftext()

It requires additional libs..

[zvn]

You mean?

imagettftext()

Sorry, imagettftext

It requires additional libs..

Maybe create a new option in zabbix.conf.php, by default it mean "use ImageString" and create new function zbxImageString with parameters like ImageString, but in case when this new option meant "use imagettftext" then zbxImageString will call imagettftext..