Optical Character Recognition. It's used for digitizing of books. This is one of the fastest possible systems, which scans an entire book in under a minute, but it produces less than perfect word formations. That's why the words seem so scrambled and skewed and are next to impossible for a computer to interpret.
That's where user input comes into play. The same unrecognizable blob is presented to hundreds of people and the most common recognition is then used in the digital text.