node 6.11 产生的验证码图片有误

[amanda94]

原来的开发环境在node 5的版本显示正常
在6版本的时候里面的字符飞掉了

[webbrain-one]

Hi there! 👋 I've opened a pull request (#10) to address this Node 6.11 compatibility issue. It fixes the bug where characters were dropping off the captcha images, ensuring they render correctly across versions. Feel free to review it when you get a chance, and let me know if you have any questions! 😊