title: QR code (2D barcode) coding and decoding algorithms?
body: <p>Looking for free/opensource code or description of algorithms to code (simple) and decode (hard) the 2D barcode <a href="http://en.wikipedia.org/wiki/QR_Code" rel="noreferrer">QR code</a>.</p>
  
  <p>It doesn't seem like a trivial problem, but it's so popular in Japan that there must be something already available...</p>