title: QR Code with empty/black center square
body: <p>I want to print a qr code with its middle portion blacked out and then print variable data on the black square (which would be none of QR code's business).</p>
  
  <p>How can I achieve that? One way could be while generating QR, I define my timing pattern or some configuration to be fixed as this centered black square.</p>
  
  <p>I'll be using my own app to decode it, so I would know the configuration while decoding as well.</p>