3 ms·

This is halftone (i.e., an apparent palette with more colors than the actual palette, by ensuring that you aren't just rounding the same way everywhere) but it

by hunter2_ 11mo ago

This is halftone (i.e., an apparent palette with more colors than the actual palette, by ensuring that you aren't just rounding the same way everywhere) but it isn't dithering in my opinion. To me, dithering means fading away the banding that occurs when the palette (or the apparent palette achieved via halftone) isn't large enough to avoid banding on its own. The halftone technique demonstrated here takes a palette of 2 colors and increases it to something on the order of 20 apparent colors, but even with 20 there are extremely obvious bands. That banding can be virtually eliminated by having way more colors (say, 256 if grayscale, 256^3 if RGB) or it can be virtually eliminated via dithering. I suspect the "error diffusion" technique (which is teased at the end of this demo) does what I'm talking about. Noise is the key to dithering, and I don't see any noise in this demo. Everything is deterministic. But the presentation is spectacular!

monitron 11mo ago
You made me curious. It looks like dithering is still an accepted name for this kind of technique: https://en.wikipedia.org/wiki/Ordered_dithering https://en.wikipedia.org/wiki/Ordered_dithering
- hunter2_ 11mo ago
  Glad I snuck in that it's just my opinion! But the article you linked to sort of admits what I'm saying: > The above thresholding matrix approach describes the Bayer family of ordered dithering algorithms. A number of other algorithms are also known; they generally involve changes in the threshold matrix, equivalent to the "noise" in general descriptions of dithering. Basically, I'm leaning into "general descriptions of dithering" with my noise requirement, and the lack of noise in "ordered dithering" leads me to consider it not-quite-dithering. The very first sentence of the general Dithering article [0] connects with my perspective as well: > preventing large-scale patterns such as color banding Aside: I probably misspoke with the word "halftone" earlier; apparently that's a specific thing as opposed to an umbrella term. I'm not sure there's a great word (other than "dither"...) for techniques to trade resolution for color. [0] https://en.wikipedia.org/wiki/Dither https://en.wikipedia.org/wiki/Dither
  - mpyne 11mo ago
    Dithering is the right term. It was called this even as far back as the Win 3.1 era where program installers typically showed you a full screen window with a background gradient that went from dark blue to black and used ordered dithering to make it look semi-respectable. The threshold map of ordered dithering is still a source of noise, it just happens to be carefully pre-baked so that (original image + noise)==output makes the output more legible than what you'd get from just mapping the original image pixels to the nearest available color. The error diffusion is static and baked into the thresholds chosen, but it's still there and choosing the error diffusion properly still matters to getting a reasonable output.
  - kragen 11mo ago
    I think that text is somewhat misleading because it leads people to believe that ordered dithering is not a kind of dithering, and also because the noise in general descriptions of dithering is not equivalent to changes in the threshold matrix. Rather, it is equivalent to differences between the input image and the output image. So I've fixed it.
__loam 11mo ago
I'm a pixel artist and everyone I know who uses this kind of technique calls it dithering.
pacaro 11mo ago
Dithering as a mechanism to reduce/remove banding can be very impressive. The color Next machines only had 12 bit displays, 4 bits per channel, but with careful use of dithering it was often indistinguishable from a 24-bit display (so called "true color")
kragen 11mo ago
Error-diffusion dithering or dithering with a precomputed blue-noise or white-noise pattern are also deterministic. One standard point of view is that what introduces noise is quantization, in the sense that the quantized image has an unwanted difference from the desired image, and dithering consists of techniques to shape that noise. The Bayer-matrix ordered dithering algorithm presented here concentrates the noise at high frequencies where the eye is less sensitive to it, but it still retains some noise at lower frequencies, which is the banding you're commenting on. Dave Long had the sharp observation earlier today that Bresenham-style line drawing is a form of dithering, where the signal being represented is the position of the pen rather than the brightness of the visual field. (I see that dreamcompiler made the same observation two days ago: https://news.ycombinator.com/item?id=45728962 https://news.ycombinator.com/item?id=45728962 but I don't know if Dave saw it there) We had a good discussion of dithering here a couple of days ago, connected with a significantly more comprehensive article with a less fancy presentation: https://news.ycombinator.com/item?id=45728231 https://news.ycombinator.com/item?id=45728231
- zozbot234 11mo ago
  > Dave Long had the sharp observation earlier today that Bresenham-style line drawing is a form of dithering, where the signal being represented is the position of the pen rather than the brightness of the visual field. Bresenham is the equivalent of a sharp quantization, with no dithering. Using true 1D dithering for line drawing would instead result in a "wobbly" almost hand-drawn output.
  - kragen 11mo ago
    It's error-diffusion dithering. You maintain an error accumulator from one pixel to the next, which keeps track of your departure from the desired slope, and you make a diagonal rather than paraxial move when it overflows. (Or is that only DDA?) But I guess you're right that the position isn't being dithered. It's the slope. I'm tempted to try the wobbly algorithm now to see what it looks like!
    - dreamcompiler 11mo ago
nmeofthestate 11mo ago
It's called ordered dithering.
caspar 11mo ago
> Dithering means fading away the banding that occurs when the palette (or the apparent palette achieved via halftone) isn't large enough to avoid banding on its own. Here[0] is a good summary of dithering/noise to reduce color banding. Interestingly, for my game[1] I found that Valve's animated dithering technique (which uses variation over time in lieu of a fixed noise pattern) worked best, as the other techniques described there altered the perceived lightness of the resulting image. [0]: https://blog.frost.kiwi/GLSL-noise-and-radial-gradient/ https://blog.frost.kiwi/GLSL-noise-and-radial-gradient/ [1]: A multiplayer Noita-like (more at https://slowrush.dev https://slowrush.dev), where the radiance-cascades-powered lighting tends to cause obvious banding patterns on really dark backgrounds.

monitron 11mo ago

You made me curious. It looks like dithering is still an accepted name for this kind of technique: https://en.wikipedia.org/wiki/Ordered_dithering https://en.wikipedia.org/wiki/Ordered_dithering

hunter2_ 11mo ago
Glad I snuck in that it's just my opinion! But the article you linked to sort of admits what I'm saying: > The above thresholding matrix approach describes the Bayer family of ordered dithering algorithms. A number of other algorithms are also known; they generally involve changes in the threshold matrix, equivalent to the "noise" in general descriptions of dithering. Basically, I'm leaning into "general descriptions of dithering" with my noise requirement, and the lack of noise in "ordered dithering" leads me to consider it not-quite-dithering. The very first sentence of the general Dithering article [0] connects with my perspective as well: > preventing large-scale patterns such as color banding Aside: I probably misspoke with the word "halftone" earlier; apparently that's a specific thing as opposed to an umbrella term. I'm not sure there's a great word (other than "dither"...) for techniques to trade resolution for color. [0] https://en.wikipedia.org/wiki/Dither https://en.wikipedia.org/wiki/Dither
- mpyne 11mo ago
  Dithering is the right term. It was called this even as far back as the Win 3.1 era where program installers typically showed you a full screen window with a background gradient that went from dark blue to black and used ordered dithering to make it look semi-respectable. The threshold map of ordered dithering is still a source of noise, it just happens to be carefully pre-baked so that (original image + noise)==output makes the output more legible than what you'd get from just mapping the original image pixels to the nearest available color. The error diffusion is static and baked into the thresholds chosen, but it's still there and choosing the error diffusion properly still matters to getting a reasonable output.
- kragen 11mo ago
  I think that text is somewhat misleading because it leads people to believe that ordered dithering is not a kind of dithering, and also because the noise in general descriptions of dithering is not equivalent to changes in the threshold matrix. Rather, it is equivalent to differences between the input image and the output image. So I've fixed it.

__loam 11mo ago

I'm a pixel artist and everyone I know who uses this kind of technique calls it dithering.

pacaro 11mo ago

Dithering as a mechanism to reduce/remove banding can be very impressive. The color Next machines only had 12 bit displays, 4 bits per channel, but with careful use of dithering it was often indistinguishable from a 24-bit display (so called "true color")

kragen 11mo ago

Error-diffusion dithering or dithering with a precomputed blue-noise or white-noise pattern are also deterministic. One standard point of view is that what introduces noise is quantization, in the sense that the quantized image has an unwanted difference from the desired image, and dithering consists of techniques to shape that noise. The Bayer-matrix ordered dithering algorithm presented here concentrates the noise at high frequencies where the eye is less sensitive to it, but it still retains some noise at lower frequencies, which is the banding you're commenting on. Dave Long had the sharp observation earlier today that Bresenham-style line drawing is a form of dithering, where the signal being represented is the position of the pen rather than the brightness of the visual field. (I see that dreamcompiler made the same observation two days ago: https://news.ycombinator.com/item?id=45728962 https://news.ycombinator.com/item?id=45728962 but I don't know if Dave saw it there) We had a good discussion of dithering here a couple of days ago, connected with a significantly more comprehensive article with a less fancy presentation: https://news.ycombinator.com/item?id=45728231 https://news.ycombinator.com/item?id=45728231

zozbot234 11mo ago
> Dave Long had the sharp observation earlier today that Bresenham-style line drawing is a form of dithering, where the signal being represented is the position of the pen rather than the brightness of the visual field. Bresenham is the equivalent of a sharp quantization, with no dithering. Using true 1D dithering for line drawing would instead result in a "wobbly" almost hand-drawn output.
- kragen 11mo ago
  It's error-diffusion dithering. You maintain an error accumulator from one pixel to the next, which keeps track of your departure from the desired slope, and you make a diagonal rather than paraxial move when it overflows. (Or is that only DDA?) But I guess you're right that the position isn't being dithered. It's the slope. I'm tempted to try the wobbly algorithm now to see what it looks like!
  - dreamcompiler 11mo ago

nmeofthestate 11mo ago

It's called ordered dithering.

caspar 11mo ago

> Dithering means fading away the banding that occurs when the palette (or the apparent palette achieved via halftone) isn't large enough to avoid banding on its own. Here[0] is a good summary of dithering/noise to reduce color banding. Interestingly, for my game[1] I found that Valve's animated dithering technique (which uses variation over time in lieu of a fixed noise pattern) worked best, as the other techniques described there altered the perceived lightness of the resulting image. [0]: https://blog.frost.kiwi/GLSL-noise-and-radial-gradient/ https://blog.frost.kiwi/GLSL-noise-and-radial-gradient/ [1]: A multiplayer Noita-like (more at https://slowrush.dev https://slowrush.dev), where the radiance-cascades-powered lighting tends to cause obvious banding patterns on really dark backgrounds.