I have, during the past few minutes, been installing and fine-tuning a reCAPTCHA engine on this blog.
When I first saw these new captchas, a year ago or so, I had no idea what the point of them was. But, as time went by, my interest of this thing grew, and today I started reading up on what it did.
A quote from the reCAPTCHA site:
To archive human knowledge and to make information more accessible to the world, multiple projects are currently digitizing physical books that were written before the computer age. The book pages are being photographically scanned, and then transformed into text using “Optical Character Recognition” (OCR). The transformation into text is useful because scanning a book produces images, which are difficult to store on small devices, expensive to download, and cannot be searched. The problem is that OCR is not perfect.
reCAPTCHA improves the process of digitizing books by sending words that cannot be read by computers to the Web in the form of CAPTCHAs for humans to decipher. 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.
You might be wondering how reCAPTCHA can know if you’re spelling the word right or wrong? It assumes that if you spell the first word right, you’re spelling the next word correct as well. Does it work? Yes, I think it does, and therefore I have added it to the comment- and contactform. Have fun digitalizing books!