QR codes are 'Super-barcodes'. That doesn't sound interesting ... but it is - and it's an interest that treads that fine line between geekiness and nerdiness (xkcd comic).
If you're using a QR code graphic, there's no need to clutter your artwork by telling people what it is and what to do with it. If they know, they know. If they don't know, they'll discover for themselves.
The qr code on the right's coloured to catch your attention - in real life these things are black and white - you read them with a code reader or mobile phone camera. They don't have to be black and white though as the built in error correction allows you to make them into something that fits with an overall design - just test that they can (probably) still be read.
Of course, if you're just using a QR code functionally, then black on white is fine. Remember the requirement for a clear border.
Their original purpose - a means to track vehicle parts - has grown to include paperwork tracking, transferring brief notes, ticketing transactions, note gathering.
Given that many people now carry mobile phones with cameras, qr codes suddenly offer a shower of ways to provide us with links to information. This can range from simple text ... to a link that automatically loads a web site.
So, qr codes can save you entering information on a keypad, in a crowd, in the street.
If the alternative is using a phone keypad, this is a real gain.
An example - a library catalogue might provide qr codes for library records. If you've a phone that can cope, you can read these straight off the display screen and capture the record for the item you've found.
A qr code at a physical location such as a display board perhaps can link to a related web site or map.
QR codes contain built-in error correction - what this means is that you don't need a perfect image of one. Up to around 30% of the pattern can be missing, badly printed, or covered with something that a seagull has done, and a QR code reader can often retrieve the messsage from the remainder.
The more text you encode, the more complicated the qr code becomes. Some mobile phones have a far better chance of decoding a qr code if it's a simple one - if you need this to be robust, stick to less than 60 characters - shorten long web addresses using a service like tinyurl. Of course, a purpose built qr code reader will cope with anything that's legitimate ...
If you're printing a qr code, ideally they need white space around them to a depth that's about equal to those large squares you'll find in three of the pattern's corners. The text in the ill-treated example on the right probably fouls that border ...
All before you, in this world, is smoke and shadows.All before you, in this world, is smoke and shadows.
Words found on a door lintel in the garden of a house in the Cretan village of Argiroupolis.
The lintel is a fragment from the city state Lappa, which occupied the same site.