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Ditherpunk: The article I wish I had about monochrome image dithering

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Re: Ditherpunk: The article I wish I had about monochrome image dithering

#71

Post by crazygringo »

enriquto wrote: post #40

This article is missing a crucial pre-processing step to dithering algorithms: apply a Retinex-like filter to enhance the local contrast before doing the dithering. This gives a dramatic improvement of the final result. In fact, by exploring the scale parameter of the pre-processing step, you find a continuous family of binarisations that interpolates between global tresholding and local dithering.

That's fascinating -- do you have any links to examples?

I'm searching online but can't find anything at all. I've never heard of using Retinex in the context of dithering, and wondering what specifically you mean by Retinex-"like"?

I'm also really curious what contexts this has been most successful in. E.g. was it used for dithering in images or games back in the 1990's when we were limited to 16-bit or 256-bit color? Or is this something more recently explored in academia or in some niche imaging applications?

Re: Ditherpunk: The article I wish I had about monochrome image dithering

#72

Post by corysama »

Cactus2018 wrote: post #12

http://www.effectgames.com/demos/worlds/ http://www.markferrari.com/ .... I recall a recent kick-starter-type blog post about a work-in-progress game with huge 2d side scrolling dither art - can't find the link but :(

Video of Mark talking about his process https://www.youtube.com/watch?v=aMcJ1Jvtef0

Re: Ditherpunk: The article I wish I had about monochrome image dithering

#73

Post by chromaton »

crazygringo wrote: post #71
enriquto wrote: post #40

This article is missing a crucial pre-processing step to dithering algorithms: apply a Retinex-like filter to enhance the local contrast before doing the dithering. This gives a dramatic improvement of the final result. In fact, by exploring the scale parameter of the pre-processing step, you find a continuous family of binarisations that interpolates between global tresholding and local dithering.

That's fascinating -- do you have any links to examples? I'm searching online but can't find anything at all. I've never heard of using Retinex in the context of dithering, and wondering what specifically you mean by Retinex-"like"? I'm also really curious what contexts this has been most successful in. E.g. was it used for dithering in images or games back in the 1990's when we were limited to 16-bit or 256-bit colo…

GIMP has it: Colors > Tone Mapping > Retinex

Re: Ditherpunk: The article I wish I had about monochrome image dithering

#74

Post by jfim »

dheera wrote: post #66
jVinc wrote: post #64

I am in the same boat as the author of having only recently played Return of the Obra Dinn between Christmas and new years. I cannot recommend it enough, if you haven't played it and like puzzlers you should pick it up. It's an extremely engaging story, and a narrative tool I have not previously encountered. No spoilers as this is revealed immediately, but essentially you are navigating past events through frozen tim…

Not in the same boat as the author but in the past few weeks I've been getting into e-Ink displays and making gadgets and framed art with them, and most of the displays I can get a hold of are either 1-bit or 4-bit greyscale, so this is super relevant. My "crude" dithering algorithm I wrote though seems not mentioned in the article. What I do is (in the case of 1-bit) just let the grey value (from 0.0=black to 1.0=wh…

You can actually combine error diffusion with your probability-based approach, which helps reduce patterns if I remember correctly (it's been a very long time).

Re: Ditherpunk: The article I wish I had about monochrome image dithering

#75

Post by linuxlizard »

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.

Re: Ditherpunk: The article I wish I had about monochrome image dithering

#78

Post by jansan »

Slightly offtopic, but this is a greate opportunity to ask what I always wanted to know. Can anybody tell me how protraits like the one in the linked article below are made? I always loved this dithering style.

https://www.wsj.com/articles/SB10001424052702304418404579467...

Edit: I found that the style seems to be called "hedcut".

Re: Ditherpunk: The article I wish I had about monochrome image dithering

#79

Post by dassurma »

linuxlizard wrote: post #75

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…

This is a lovely compliment. Thank you for taking the time to write it :)

Re: Ditherpunk: The article I wish I had about monochrome image dithering

#80

Post by dassurma »

ohazi wrote: post #68

> As this image shows, the dithered gradient gets bright way too quickly. sigh Not in Firefox on Linux. I vaguely recall seeing a multi-year-old bug related to subtly broken gamma behavior in either Firefox or Chrome, but can't seem to find it right now.

Ah, this happens when Firefox/Chrome scales the image. I added a note to the article a couple hours ago, not sure if you saw that.

If you open the image in question in a new tab (to prevent any scaling) you’ll see the image as intended with the “desired” effect.

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