I'm pretty sure that I mentioned the printer tracking dots to the researchers at the lab and certainly mentioned DataGlyphs. So they were aware of alternatives. The trick is to get a workable system with cameras that have the resolution to pick out those details from a dozen feet away, as well as a software stack that can recognize them at ~60fps.

The goal has always been to move away from the dots, you can see this in the progress report: https://dynamicland.org/2019/Progress_report/

That said, and this is purely my opinion, the system works well enough as it is, and there is so much fun stuff to build on top of what works, that it's hard to prioritize a better object recognition system over the myriad of other interesting things to be done.

I imagine it would very difficult to read these dots from a distance and dynamically. I just mention it because most printed documents already have indentifiers printed on them that don't require seeing individual fibers.

Ah, noted! With that in mind, did you know that those printer dots are what the team that won the 2011 DARPA Shredder Challenge used to win?

https://en.wikipedia.org/wiki/DARPA_Shredder_Challenge_2011

Fun fact: Otavio Good, who led the winning team, learned about the printer dots on this very site. As I recall, he said that the dots were like a map that let them reconstruct the shredded documents.

I would had thought, even then, that this was not only commonly known, but not the sole only annulment/rule among a generally "rules-free" competition, having been rather obvious, especially to the audience these competitions attract.

Thank you for reminding me, and others, how immediate and obvious success can be.

Is there a better source that talks about it? Didn't see it mentioned on that page.

I'm not sure if there's a source online as I learned about it from Otavio directly. The slightly longer story, as I recall it, is that their team basically built a "game" to help humans unshred documents, and was using that approach until Otavio happened to read about the printer dots on HN. He updated his code to take those into account and was astonished at how helpful they were.

Oh, that’s why my HP inkjet refuses to print a black & white page when it’s low on yellow.

Not entirely it also uses bits of color ink to make the black and white page look better, at least according to the printer companies who conveniently also benefit by selling you more ink.

How can it make black look better by adding yellow to it?

Black ink isn't perfectly black. Adding other colors of ink makes it darker. If you don't really care about how dark the result is, the term you're probably looking for in settings is "rich black."

There is a few bits you can flip on the Firmware side to fix that.

Woah! I never considered that until now. I'll bet you're right.

> But then, how do B&W laser printer allow for tracing ?

They don't, because they don't need to. The point of the yellow dots is to prevent the printing of counterfeit currency, which itself tends to require the use of more ink colors than only black. It's probably possible to refill a "black" ink/toner cartridge with the exact shade of green (or whatever) to replicate the color of a currency note, but if it was easy to do then there'd probably be a lot more counterfeit bills floating around.

The ink/toner is also half the battle. The other half is the paper, since obviously the US Treasury doesn't use ordinary printer paper to print $20 bills. The usual trick is to take a $1 or $5 bill, bleach it (or otherwise remove the existing printing), and print a $20 bill design onto it - but that's easier said than done, due to both the ink/toner color issue mentioned above and due to the difficulty of getting the donor bill exactly aligned (and doing so again, in the exact same way, for the other side of the bill).