QR Code: Barcode of Steal

Ok, not quite. But did you know that QR codes have some of the highest read rates?

QR codes use a Reed-Solomon error correction based technology in order to help recover from errors in scanning.

You may have noticed that three of the four corners of a QR code are square blocks—these are what the barcode reader uses to coarsely identify and align the code. In addition, the Quiet Region, what appears to be a blank area around the edge of the code, is used to help the barcode reader decipher the code from the background image.

A variety of different masks can be applied to the encoding—the specification of the mask is stored in the format information. Masks slightly alter the appearance of the QR code. Even if QR codes contain the exact same data, they could appear differently based upon the mask used. The ideal mask is one that minimizes the appearance of large blocks of the same color, which can cause issues for the barcode reader.

The Reed-Solomon error correction algorithm allows for four configurable error correction levels—the higher the error correction level, the less storage capacity. There are four levels available:

  • L (low) 7% of codewords can be restored
  • M (medium) 15% of codewords can be restored
  • Q (quartile) 25% of codewords can be restored
  • H (high) 30% of codewords can be restored

I recently came across an article in which a researcher created an H version of a QR code and skewed it in a variety of different ways, changing rotation, contrast, color, blur, noise and adding effects.

But, I don’t want to ruin your fun. You can view all of the different effects used and see if they scan correctly, or better yet… scan them yourself to find out! The results may surprise you. Happy scanning!

qr code