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by komlan 880 days ago
Physically bigger pixels help a lot indeed. The encoding mode also helps make pixels bigger.

This is very convenient when you control the QR reader and need to represent long numeric identifiers like UUIDs.

For example:

  9728983f-7d7d-4189-b624-f92781e36650 (lowercase UUID):
    => length=36, 15 pixels between markers
  JWM9GFVXFN0RKDH4Z4KR3RV6A0 (base32 UUID):
    => length=26, 11 pixels between markers
  9728983F-7D7D-4189-B624-F92781E36650 (uppercase UUID):
    => length=36, 11 pixels between markers
  200924207194334734815443970355691218512 (decimal UUID):
    => length=39, 7 pixels between markers
The uppercase UUID has bigger pixels because it used a different encoding, and gets the same results as the shorter base32 uuid.

The decimal UUID is a longer string, but results in much bigger pixels because it can use numeric encoding.

I have a QR code base attendance tracker [1], where attendees show the code [2] on their phones (glares, etc.), in bad lighting conditions, etc. Bigger pixels means scanning stays quick. Same with parcel tracking [3] where field agents might need to scan QR codes in barely-lit hallways, etc.

[1] https://workspace.google.com/marketplace/app/qr_code_pass_fo...

[2] https://share.darkaa.com/!qntvtzNPWJ

[3] https://admin.trak.codes/
1 comments
lifthrasiir 880 days ago
You can also use base45 [1]:

  -4J5BJ+%F$C881NIMV-IG2.C (base45, 132 bits in QR)
  JWM9GFVXFN0RKDH4Z4KR3RV6A0 (base32, 143 bits in QR)
  200924207194334734815443970355691218512 (decimal, 130 bits in QR)
It will make use of all allowed characters in the alphanumeric mode, while being significantly shorter than base32 and as dense as decimal. And decimal encoding in general needs bignum, because there is no suitable 10^k which is only slightly larger than powers of two so no convenient binary-to-decimal encoding exists (conversely, QR code itself does make use of the fact 2^10 is only slightly larger than 10^3 for this mode). Base45 always works on three-byte groups and maintains the similar efficiency in comparison.

[1] https://datatracker.ietf.org/doc/html/rfc9285

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komlan 880 days ago
That's neat, especially for arbitrary binary data!
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