You must have an screenshot tool and an OCR tool. The tools I use is imagemagick to take screenshots and gocr to recognize characters.

import -quality 100 /tmp/scan.png && gocr /tmp/scan.png

For example, testing with this example the output was:

Linux, ubuntu, gentoo, scripts, security, networks, digg, sIashdot, engadget, youtube.

Doesnt work 100% but can be usefull :)