Actually swirls are very reversible - http://news.bbc.co.uk/1/hi/7384834.stm http://news.bbc.co.uk/1/hi/7384834.stm (Paedophile caught from video with swirled o

Actually swirls are very reversible - http://news.bbc.co.uk/1/hi/7384834.stm http://news.bbc.co.uk/1/hi/7384834.stm (Paedophile caught from video with swirled obfuscation of his face.) You're definitely right about adding entropy though, but why bother? Just blacking it out guarantees how much information is available - zero.