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How a QR code still works with a hole in the middle.

A QR code stores not just your data but Reed-Solomon check data too – like the check digits of an IBAN, only far more of them. Depending on the level (L, M, Q, H), 7, 15, 25 or 30 percent of the pixels can be reconstructed. The three big squares in the corners only tell the scanner which way is up and how skewed its view is.

Useful: A logo in the middle of a code works because the designer chose level H.

Source: en.wikipedia.org

AlltagCodesInformatik

Difficulty:

Question on this card

What are the three big squares in the corners of a QR code for?

  1. They hold the actual data
  2. They store the check data
  3. They help the scanner find orientation and position
  4. They show the code's version
Show the answer

Correct: They help the scanner find orientation and position

The finder patterns give position and distortion; data and check data live in the rest of the code.

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