问题
I am developing a registration form in that i want to place the CAPTCHA . i generate a random string but how to convert that into the image other wise how can i develop the CAPTCHA code or any reference. thank you
回答1:
Try out reCaptcha or check out eh blog post "Captcha Using Asp.Net" which I wrote sometime back.
回答2:
While having a captcha may feel like a good feature, it really isn't: Nowadays there's huge swarms of labor houses in China and such where people are paid for successfully filling out captchas. Yes, that means there's thousands of people manually breaking the system all the time.
If I were implementing my own registration protection/antispam system, I'd go with the more cultural one choice which is just a variation of magic words. What I mean that instead of showing barely readable garble, I'd add a small intellectual puzzle and a text field for it's answer, for example asking how much is seven plus six minus one is currently a lot better at detecting both bots and stupid users.
来源：https://stackoverflow.com/questions/1768582/how-to-write-the-captcha