找了半天 问题权限什么的都OK
最后发现是服务环境少了GD库
登录网站后台再下起始页的下面显示的系统信息里面可以看到是否缺少 GD库
我用的是WHM面板就很方便的升级了下就OK了
You can install this using Easy Apache in cPanel by going to Home > Software > EasyApache and Choosing the Option to Build based on Customized Profile and under the Exhaustive Options list select GD.