开启验证码登录后验证码图片不能显示已解决悬赏30积分

11:03:38 Uncaught Error: Call to undefined function imagettfbbox() in /opt/zbox/app/zentao/lib/captcha/captcha.class.php:340
Stack trace:
#0 /opt/zbox/app/zentao/lib/captcha/captcha.class.php(454): captcha->writePhrase(Resource id #49, 'cK7ZE', '/opt/zbox/app/z...', 150, 40)
#1 /opt/zbox/app/zentao/module/misc/control.php(236): captcha->build()
#2 /opt/zbox/app/zentao/framework/base/router.class.php(1759): misc->captcha('captcha', '')
#3 /opt/zbox/app/zentao/www/index.php(72): baseRouter->loadModule()
#4 {main}

在php日志中看到了验证码

请问Call to undefined function imagettfbbox() 这种如何解决

试下给整个zentao目录递归设置下读写权限，然后再试试