如何在asp.net核心Asp.net Mvc 6中创建验证码？

I am developing asp.net MVC 6 application in asp.net core , and i want to create a captcha for my login page. in previous .net frameworks i used the system.drawing to create a captcha but since in .net framework core we dont have system.drawing , how can i achieve this ?I am developing asp.net MVC 6 application in as