Попробуйте использовать imagettftext.
<?php
// http://localhost/test.php?text=احسان
// test.php file
$font = 'C:/Windows/Fonts/Arial.ttf';
$text = $_GET['text'];
// [switch to right to left]
// try comparing of using this block and not using this block
$rtl = array();
for($i=0; $i<strlen($text); $i+=2) {
$rtl[] = substr($text, $i, 2);
}
$rtl = array_reverse($rtl);
$rtl = implode($rtl);
$text = $rtl;
// [/switch to right to left]
$im = imagecreatetruecolor(65, 35);
$black = imagecolorallocate($im, 0, 0, 0);
$white = imagecolorallocate($im, 255, 255, 255);
imagefilledrectangle($im, 0, 0, 500, 100, $white);
imagettftext($im, 12, 0, 10, 20, $black, $font, $text);
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);