CAPTCHA stands for "Completely Automated Public Turing test to tell Computers and Humans Apart". It is a type of challenge-response test used to determine whether the user is human or not. The document discusses the origins of CAPTCHA, different types of printed and image-based CAPTCHAs, how they work, examples, and challenges with breaking CAPTCHAs.

1. CAPTCHA What humans can do, But computers can not.

11. Example showing H-CAPTCHA

14. GIMPY Examples EZ-GYMPY R-GIMPY

18. Face Recognition CAPTCHA

24. Free Email Registration Hotmail Registration Yahoo! Registration

26. Different CAPTCHA’s

27. Thank You!

29. OCR (Optical Character Recognition ) The machine recognition of printed characters. OCR systems can recognize many different OCR fonts, as well as typewriter and computer-printed characters. Advanced OCR systems can recognize hand printing. When a text document is scanned into the computer, it is turned into a bitmap, which is a picture of the text. OCR software analyzes the light and dark areas of the bitmap in order to identify each alphabetic letter and numeric digit. When it recognizes a character, it converts it into ASCII text. Hand printing is much more difficult to analyze than machine-printed characters. Old, worn and smudged documents are also difficult. Scanning documents and processing them with OCR is sometimes as much an art as it is a science.

30. OCR

31. Segmentation It is nothing but Image Processing Pixel based Segmentation Model based Segmentation Multi-scale Segmentation Semi-automatic Segmentation