求高手指点,thinkphp3.2.3验证码显示的代码，官方开发手册里面的方法用了不知道什么原因无法显示验证码 Call to undefined function Think\imagettftext() 错误位置 FILE: /storage/emulated/legacy/www/3.2.2888888888888888/ThinkPHP_3.2.2_full/ThinkPHP/Library/Think/Verify.class.php 　LINE: 166 ThinkPHP3.2.2 { Fast & Simple OOP PHP framework } -- [ WE CAN DO IT JUST THINK ]

<?php
namespace Home\Controller;
use Think\Controller;
use Think\Verify; class IndexController extends Controller {
public function index(){
echo '123456';
}
public function Verify(){
$Verify = new \Think\Verify();

$Verify->entry();

}

}

访问！http：//192.168.42.129：8080/ThinkPHP_3.2.2_full/index.php/home/index/verify