Comment by linuxlizard
5 years ago
Back when I worked at Marvell Semiconductor (circa 2005), we made laser printer ASICs for HP. We did a lot of dithering in hardware. We had a hardware block that did error diffusion, we had a hardware block that did regular diffusion. We also had a hardware block that did Blue Noise. I was responsible for implementing the firmware that drove those printers' scan/copy path: scan an image in monochrome, run through the dither hardware to create the bit pattern fed to the laser engine.
No one could explain to me how to use the blue noise block. I couldn't understand what the blue noise block was doing. This is the first article that explained, in terms I could understand, how blue noise dithering works.
I can die happy. Thank you.
This is a lovely compliment. Thank you for taking the time to write it :)
Thank you for such a great blog post that even years later, I could catch up and understand!
(We never did turn on the blue noise block. Even today, it sits idle. Sad.)
Folks interested in learning more about dithering in genreal or blue noise dithering in particular should read Bart Wronski's blog posts here:
https://bartwronski.com/2016/10/30/dithering-in-games-mini-s...
Now that's amazing. Not only because it was hardware based, but because you were solving a real problem, a limitation, instead of just aesthetic endeavor. It was an engineering solution. There is a lot of aesthetic beauty in mundane engineering, rarely seen by anyone. So kudos to designers to pick out something interesting and giving it the light :) It's all cool.
There is no math.Random() in hardware, so I have to ask: what algorithm did the noise block use? :)
Not the OP, but since repeatability is not a problem you can just use any cheap and insecure random number generator and hardcode a constant for the seed.
The period needs to be sufficiently long such that it won’t show up as visible artifacts. I would think something like PRBS23 would do the trick and be trivial to implement.
That’s the cheapest choice. Better whiteness could come with some added complexity.
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We had to generate values in firmware then populate a LUT. IIRC we just used a simple pseudo-random number generator from the C library. Non-crypto so it didn't matter too much.
Well, LFSR RNG-s are pretty efficient in terms of HW space. You take a single-bit wide shift registers of length n, and feed back its output to the beginning XOR-ed with predefined bits in the shift register.