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Image Dithering: Eleven Algorithms and Source Code

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Re: Image Dithering: Eleven Algorithms and Source Code

#51

Post by c3534l »

pjc50 wrote: post #50
c3534l wrote: post #44

Earlier quoted context omitted.

I find it amusing that someone would have a dedicated GPU, yet cannot fully render color images. I mean, I'm sure there's actually plenty of use-cases, but it's still funny.

"Fully render" is a strange way of putting it - most consumer hardware has only 8-bit colour depth, and lots of video compression algorithms will turn smooth gradients into blocky messes that would benefit from dithering. If you're processing the decode at 10 or 16 bits and need to render at 8 bits, it's much better to dither than truncate.

Fair enough. I don't think I've ever actually programmed a GPU with the purpose of making images, so my terminology might not be the most precise.

Re: Image Dithering: Eleven Algorithms and Source Code

#52

Post by rasz_pl »

dividuum wrote: post #30

There is another interesting application for dithering that I've read about in the recent Uncharted 4 Brain Dump (Ctrl-F for "Dithering") here https://redd.it/4itbxq : Use dithering instead of alpha blending to fade out close objects. Alpha blending can be quite expensive while dithering just omits pixels. The result looks like this: http://allenchou.net/wp-content/uploads/2016/05/dithering-1-... (best visible at the…

this is ugly as heck, sega saturn did the same

http://www.mattgreer.org/articles/sega-saturn-and-transparen...

Re: Image Dithering: Eleven Algorithms and Source Code

#53

Post by the8472 »

pjc50 wrote: post #50
c3534l wrote: post #44

Earlier quoted context omitted.

I find it amusing that someone would have a dedicated GPU, yet cannot fully render color images. I mean, I'm sure there's actually plenty of use-cases, but it's still funny.

"Fully render" is a strange way of putting it - most consumer hardware has only 8-bit colour depth, and lots of video compression algorithms will turn smooth gradients into blocky messes that would benefit from dithering. If you're processing the decode at 10 or 16 bits and need to render at 8 bits, it's much better to dither than truncate.

> and lots of video compression algorithms will turn smooth gradients into blocky messes that would benefit from dithering.

More accurately: Either you have a 10bit-per-channel video (or better) which has smooth gradients which will need dithering when rendering to an 8bit-per-channel display.

Or you have 8bit video (more common) which will have to be passed through a debanding filter first. But then how do you get the debanded result onto the screen without reintroducing the banding? By dithering it.

Re: Image Dithering: Eleven Algorithms and Source Code

#54

Post by EdHominem »

rabidsnail wrote: post #48
spiderfarmer wrote: post #25

Earlier quoted context omitted.

This is othering for anyone who is not a heterosexual man I disagree. Women look at other women as well. It's very natural to feel excluded when groups of people over something you don't get excited about, whatever the subject. If, for example, people can contain their excitement about Magic cards when I'm around, I'm fine. There is a long tradition of sexual images, suggestions and approaches being used to shame, sc…

Forget abstractions for a second; there are people whom this makes uncomfortable (we know because they said so), and the cost of that is much higher than the very small benefit of using one image over another as a test image. Simple cost/benefit analysis says to use something else.

Obviously in certain circumstances only - few of us here would censor Charlie Hebdo.

We only care about discomfort that we think is reasonable, or more accurately, not a lie designed to control the actions of others.

In this case, most people agree that sexualizing the workplace is a strong negative and are in agreement with you. But as a general rule, you'd have much less support.

Re: Image Dithering: Eleven Algorithms and Source Code

#55

Post by rasz_pl »

Neat facts:

-3DFX Voodoo (all models in 16bit color depth) let you enable hardware dithering block (2x2/4x4 ordered dither, zero performance penalty). They did it to save framebuffer space (24bit textures, 16bit framebuffer). It made 3dfx graphics look significantly better than nvidia/ati in 16bit depth. Earlier cards used 4x1 filter on the output, Banshee and later models gained 2x2 filter providing "22 bit like quality" as 3dfx called it.

-Back in ~1994 some HP unix workstations used dithering to produce 'near 23bit color' out of 8bit framebuffer https://en.wikipedia.org/wiki/HP_Color_recovery

-All crappy (TN) LCD panels (staple of garbage bin supermarket 1366x768 laptop, and older 'gaming' fullhd ones) use FRC which is a form of temporal dithering https://en.wikipedia.org/wiki/Frame_rate_control

One legitimate use of dithering was in the days of CGA/EGA/other fixed palette hardware. You can relive it here 'Joel Yliluoma's arbitrary-palette positional dithering algorithm': http://bisqwit.iki.fi/story/howto/dither/jy/

Re: Image Dithering: Eleven Algorithms and Source Code

#56

Post by rabidsnail »

EdHominem wrote: post #54
rabidsnail wrote: post #48

Earlier quoted context omitted.

Forget abstractions for a second; there are people whom this makes uncomfortable (we know because they said so), and the cost of that is much higher than the very small benefit of using one image over another as a test image. Simple cost/benefit analysis says to use something else.

Obviously in certain circumstances only - few of us here would censor Charlie Hebdo. We only care about discomfort that we think is reasonable, or more accurately, not a lie designed to control the actions of others. In this case, most people agree that sexualizing the workplace is a strong negative and are in agreement with you. But as a general rule, you'd have much less support.

General rules aren't good for very much other than arguing with people on hacker news.

Re: Image Dithering: Eleven Algorithms and Source Code

#57

Post by spiderfarmer »

rabidsnail wrote: post #48
spiderfarmer wrote: post #25

Earlier quoted context omitted.

This is othering for anyone who is not a heterosexual man I disagree. Women look at other women as well. It's very natural to feel excluded when groups of people over something you don't get excited about, whatever the subject. If, for example, people can contain their excitement about Magic cards when I'm around, I'm fine. There is a long tradition of sexual images, suggestions and approaches being used to shame, sc…

Forget abstractions for a second; there are people whom this makes uncomfortable (we know because they said so), and the cost of that is much higher than the very small benefit of using one image over another as a test image. Simple cost/benefit analysis says to use something else.

   I totally did not intend to put it to the floppy disk...
So he didn't mean to turn it in. But what he does in his own time, isn't that his business?

Your analysis also tells us that you should not look at porn in your own free time, as the potential cost is much higher because it makes 2 parties uncomfortable, if caught.

Re: Image Dithering: Eleven Algorithms and Source Code

#58

Post by startling »

spiderfarmer wrote: post #57
rabidsnail wrote: post #48

Earlier quoted context omitted.

Forget abstractions for a second; there are people whom this makes uncomfortable (we know because they said so), and the cost of that is much higher than the very small benefit of using one image over another as a test image. Simple cost/benefit analysis says to use something else.

I totally did not intend to put it to the floppy disk... So he didn't mean to turn it in. But what he does in his own time, isn't that his business? Your analysis also tells us that you should not look at porn in your own free time, as the potential cost is much higher because it makes 2 parties uncomfortable, if caught.

And he received extra points for it.

Re: Image Dithering: Eleven Algorithms and Source Code

#59

Post by bitshiftthis »

startling wrote: post #5
mynegation wrote: post #4

Back when I was at university, we had a computer graphics course. Each week we got new assignment that we needed to program, write to a floppy disk (it was before Internet became widely available) and give it to the prof next week. Dithering was one of the assignments. We were required to implement black-white quantization and then Atkinson and Floyd-Steinberg. We were given the freedom to choose our own images. Duri…

Gross.

Is this a joke post lol? Grow up kid. This isn't even remotely offensive.

Re: Image Dithering: Eleven Algorithms and Source Code

#60

Post by kalleboo »

joosters wrote: post #34

Has anyone tried using the equivalent of animated GIFs to help with dithering? If you have a limited palette of colours, perhaps you could produce two dithered versions, with pixels sometimes having different colours in alternate frames. If the image is refreshed fast enough, two colours could blend into a third. The most extreme example could be 'dithering' a grey square into 1) a black square and 2) a white square,…

> The most extreme example could be 'dithering' a grey square into 1) a black square and 2) a white square, and when they are rapidly switching between the two it might appear as a grey instead.

I remember seeing old STN grayscale LCDs that seemed to work like this (and I even implemented it myself on the TI-83 as a test)

edit: looks like is called "Frame Rate Control" and used to be common http://robotics.ee.uwa.edu.au/eyejr/lcd/FRC-information.pdf

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