I’ve been intrigued with QR codes for a while now as they are in effect 2-dimensional barcodes; a way of storing information that can be retrieved by digital scanning devices.

Normally we think of barcode scanners as laser powered devices that checkout operators use to scan our peaches but, when reduced to its core functionality, it is basically just a device that can tell the difference between dark and light and interpret the code.

What the Japanese realised a long time ago was that we already have such a device in our pocket in the form of a mobile phone with a camera which has exactly the right fundamental functions to be a code reader; these being a camera and some way of programmatically interpreting images, usually in the form of a Java application.

In Japan you will find that QR codes are used extensively on advertising posters and the like to provide additional information such as contact numbers & URL links (web access via mobile networks is de rigeur in Japan after all), or to send special promotions, e.g. 20% discount if you show this message in-store.

QR codes can store much more information than normal barcodes, up to 4K, and when you consider that this post is less than half of that, you can begin to see the potential. Imagine scanning the QR-code of a new book from a tube poster which gives you a sample chapter to read on the way to work; or imagine rotating digital displays containing news items which you can take photos of and store, to read later. In reality however, I’ve had difficulty in getting a mobile phone camera (well they’re not really renowned for their optical quality) to interpret codes of anything near that length.

So whilst everyone else in London was sunning themselves on the hottest weekend of the year and I was stuck indoors with an (almost) broken leg, I started thinking about this from a different perspective: how ‘dirty’ can my code be before my phone will interpret it? So out came the felt tip pens and I started drawing a code manually on several pieces of graph paper which I subsequently taped together.

Initial result were somewhat disappointing with the camera being unable to read my secret code, until I realised that it might be a colour/contrast issue; I had drawn my barcode in blue. And indeed photocopying my original handiwork in black and white resulted in an image which was picked up instantly by my decoder.

I look forward to investigating the error correction facilities of QR codes further, but in reality, I would prefer to be out in the sun.

You can download QR code readers for several phones here.

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