Is there any DECAPTCHA library in .NET?

Question

I'm looking for some sample projects to read CAPTCHA images. Is there any in C# or VB ?

pseudo code:

String captchaText = CaptchaDecoder(Image captchaImage);

Answer 1

Take a look to:

Text-based CAPTCHA Strengths and Weaknesses. ACM Computer and Communication security 2011 (CSS’2011). link

The authors present a CAPTCHA breaker and explain a generic algorithm to crack standard CAPTCHAs

In this section we present our captcha breaker, Decaptcha, which is able to break many popular captchas including eBay, Wikipedia and Digg [...] Decaptcha implements a refined version of the three stage approach in 15,000 lines of code in C# [...]

Answer 2

This is easier said than done.

This involves either brute-forcing the captcha or running OCR algorithms on it to try and detect what is written in the captcha.

You might want to check this related question: Has reCaptcha been cracked / hacked / OCR'd / defeated / broken?

It also depends on what techniques were used to produce the CAPTCHA. Some distort the text and some squeeze the text.

Your question is a little vague.

Additional reading here: http://en.wikipedia.org/wiki/CAPTCHA

• Christian