Re-captcha :

All know about the captcha ,where some junk images containing distorted characters are put in many web pages for human identification. The only benefit is the web masters can identify the spammer scripts. But for the million's of real users its mear wastage of time. So to make use of such human resource here comes the new technique called ReCaptcha. Here we go for it ...


There are many number of useful old books written by authors in hand are available in library , but what is the use in this 21st century of having book in paper-book format. The only medium available is Internet for effective sharing of knowledge. Since there is no effective artificial algorithm available to scan those scanned images of the books, it really hard to digitize them. Here our Recaptcha technique make use of above said human resources in useful way to digitize those books.

OCR can do only this thing :

reCAPTCHA improves the process of digitizing books by sending words that cannot be read by OCR to the Web in the form of CAPTCHAs for humans to decrypt, It is mutually beneficial , web masters can crack the spammers and importantly on the other end old books are getting digitized. More specifically, each word that cannot be read correctly by OCR is placed on an image and used as a CAPTCHA. This is possible because most OCR programs alert you when a word cannot be read correctly.

Here comes the cleverness of Recaptcha technique and little disadvantage for web masters :

If a computer can't read such a CAPTCHA, how does the system know the correct answer to the puzzle? Here's how: Each new word that cannot be read correctly by OCR is given to a user in conjunction with another word for which the answer is already known. The user is then asked to read both words. If they solve the one for which the answer is known, the system assumes their answer is correct for the new one. The system then gives the new image to a number of other people to determine, with higher confidence, whether the original answer was correct. Yeah its good and clever ,but till then this technique confirms from many no of people ,there is always a chance for spammers to prove their point of surveillance.

Currently, REcaptcha are helping to digitize books from the Internet Archive and old editions of the New York Times.

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