php GD库中文乱码的解决方法

<?php
$pic=imagecreate(250,30);
$black=imagecolorallocate($pic,0,0,0);
$white=imagecolorallocate($pic,255,255,255);
$font="C://WINDOWS//Fonts//simhei.ttf"; //必须是字符的路径
$str ='php'.iconv('gb2312','utf-8','面对对象')." bbs.it-home.org";
imagettftext($pic,10,0,10,20,$white,$font,$str);
?>

<?php
/**
 * GD库应用 文字水印
*/
$pic=imagecreate(250,30);
$black=imagecolorallocate($pic,0,0,0);
$white=imagecolorallocate($pic,255,255,255);
$font="C://WINDOWS//Fonts//simhei.ttf";
$str ='php'.iconv('gb2312','utf-8','面对对象')." bbs.it-home.org";
imagettftext($pic,10,0,10,20,$white,$font,$str);

header("Content-type: image/jpeg");
$filename='../src/images/photo.jpg';
$im=imagecreatefromjpeg($filename);
imagecopymerge($im,$pic,0,0,0,0,250,30,50);
imagejpeg($im);
?>