What time is it?

Comments

• ChaoticNeutralCzech@feddit.org ⁨13⁩ ⁨hours⁩ ago

  time.gov

  Yes it’s already scannable…

  Why wouldn’t it be? I’ve drawn 2 QR codes on graph paper already and of course they work.

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  • over_clox@lemmy.world ⁨1⁩ ⁨hour⁩ ago

    Curious I am now, trailing slash?

    This wasn’t encoded with a trailing slash, nor does the scanner app I use decode it with a trailing slash.

    I’m not sure, but if it is decoding with a trailing slash on your side, that might be your scanner app doing that automatically.

    Formally speaking, coming from the dialup internet days, full proper URLs were meant to end in a trailing slash, and if you didn’t type the trailing slash in yourself, some web browsers would have to ping the site twice before it figured out it needed that trailing slash, slowing down website loading time.

    I dunno, thank goodness the internet has evolved enough where www.time.gov can be simplified to time.gov

    On my end, my web browser itself (Fennec, a fork of Firefox), put the trailing slash in on its own… 🤷

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  • Warl0k3@lemmy.world ⁨9⁩ ⁨hours⁩ ago

    Yeah the QR standard is astoundingly resilient to noise. iirc the highest redundancy can still be read with 60% of the glyph obscured, it’s really a fascinating protocol.

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    • ChaoticNeutralCzech@feddit.org ⁨7⁩ ⁨hours⁩ ago

      Nah, it’s 30%, and very much depends on how the damage is laid out.

      • The corner squares (finder patterns) must keep a ⬜⬛⬜⬛⬛⬛⬜⬛⬜ cross-section at most angles. Most readers will accept even round ones. This applies to the smaller squares (alignment patterns) on larger QR codes too.
      • The zebra strips ⬛⬜⬛⬜⬛ (“timing patterns” if you’re a nerd) connecting the finder patterns must remain intact. Very few readers can correct for errors in that.
      • At this point, a good reader will be able to detect the QR code’s position in the image and its resolution (“version” if you consume ISO propaganda), and thus calculate the location of every pixel (“element”, ditto). Each of those will usually be sampled at a radius of around ⅓ of the distance between them. This allows for slightly wavy codes but also codes with rounded pixels or even unrelated content in the edges. (For the record, this is lazy and I prefer this version of the concept that uses almost up-to-spec QR codes.) Google Lens is more sophisticated than just using a 3D perspective transform, as I already mentioned.
      • One line of pixels around finder patterns is necessary for decoding (mask and ECC level info) and has basically no error correction so it should be also clear except the ⅓²=⅑ trick described above.
      • The data is stored with robust Reed-Solomon correction, which is byte-wise. You can safely cover about half of the advertised recoverable area with contiguous damage anywhere except the sections mentioned above. Still, you can damage more area by taking several things into account:
        • Know how the data is laid out in the specific QR resolution, and keep in mind that Reed-Solomon is bytewise. Thus, you want to damage as few bytes as possible, and for most total area, the strategy is to ruin all 8 bits in each. Without deeper analysis (looking up the byte layout), a good rule of thumb is that vertical damage aligned to an even number of columns from the right (skipping Column 7 with the vertical zebra stripe and thus no data) is likely to ruin the least amount of bytes partially.
          • Looking up the byte layout will also reveal that there are probably 1-7 unused pixels in the leftmost two columns, probably arranged like ⡿ in the very top of the data portion (Row 10 and below). These can be damaged without consequence!
        • Damage whose very dark spots line up with original black pixels (and vice versa) does not really count. Keep in mind that while using this strict definition of damage results in way fewer damaged bits, those are most likely not contiguous, so only a few 8-bit bytes will remain intact through this.

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    • FishFace@lemmy.world ⁨9⁩ ⁨hours⁩ ago

      With hand drawn codes it’s also that the scanners are very good. It’s no good having high redundancy if the scanner can’t transform the 3D code to a square and find the timing bits etc

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  • over_clox@lemmy.world ⁨13⁩ ⁨hours⁩ ago

    I’m trying to confirm this shit even works before I get it tattooed on my wrist at a 1mm per square scale…

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    • JackbyDev@programming.dev ⁨7⁩ ⁨hours⁩ ago

      Hey OP, I’ve seen a lot of tattoo artists recommend not getting QR codes tattooed because they fade and smear over time. Also, I don’t wanna sound overly dramatic, but with the current political landscape being to aggressively cut government programs, I wouldn’t trust a domain name being around forever. It may still be better for the code to be one you control (they’re like $12 a year) and set it to redirect there instead.

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    • ChaoticNeutralCzech@feddit.org ⁨13⁩ ⁨hours⁩ ago

      Print one out at 1:1 scale and wrap it around your wrist, then test it. Curved surfaces are challenging for QR code readers. AFAIK Google Lens is one of the best ones (it will follow edges of pixels in wavy codes) but you’ll want any old open source one to work.

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    • crumbguzzler5000@feddit.org ⁨13⁩ ⁨hours⁩ ago

      Tattoos can get a little blurry over time, especially when they are really small. Look at examples of people who get little quotes or words written in cursive, sometimes they become almost unreadable.

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• jqubed@lemmy.world ⁨14⁩ ⁨hours⁩ ago

  Wouldn’t that have been easier on grid paper? Why use ruled paper?

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  • ideonek@piefed.social ⁨13⁩ ⁨hours⁩ ago

    They drew QR code by hand. Do we realy think the ease was a factor here?

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  • over_clox@lemmy.world ⁨14⁩ ⁨hours⁩ ago

    I didn’t have ruled paper handy. Ideas came to mind, and I just wanted to start sketching like immediately.

    Yes awkward, but also kinda helps relieve my stress as well…

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    • Tetsuo@jlai.lu ⁨9⁩ ⁨hours⁩ ago

      Having to do a QR code without a grid would have the opposite effect of “relieving stress” for me :)

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• Marty_TF@lemmy.zip ⁨13⁩ ⁨hours⁩ ago

  it’s tonga time.

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