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Websites should not use dithered images

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Re: Websites should not use dithered images

#51

Post by robertlagrant »

louissan wrote: post #20
deltarholamda wrote: post #16

Earlier quoted context omitted.

This is what I think of when the dithering articles show up. Way back in the day, dithering and reducing the color palette made a difference, when you were talking images loading over a 28.8k modem. For many widgets, you could shave kilobytes off, when kilobytes really, really meant something.

well tbh they still do today. Every byte you can take off (very easily at that ...) makes websites: . faster to the user, which does contribute to a general reduced level of stress :-) . use less energy: less bandwidth/less CPU (cisco, nginx, your disk/memory cache.... you name it). Less $$ on your bandwidth/cpu bill @[insert cloud provider here] and less BW/CPU used up on your user's mobile metered connection (becau…

They do matter, but not as much as when websites loaded at 0.25kB/s.

Re: Websites should not use dithered images

#52

Post by efields »

If you're at the point of "should I use dithering" to optimize your website, congratulations: you're in the 99th percentile of optimized websites.

You're already a SSG PWA with modular js and a stylesheet devoid of unused selectors.

You've got almost all the unlocks. How much longer do you really want to be playing this game?

Re: Websites should not use dithered images

#53

Post by dev_tty01 »

DitheringIdiot wrote: post #32

nathaniel here, writer of the article this article is referencing. If it's okay with you I'll update the original with a link to this at the top. It's sort of hilarious that I made an whole app based on a premise that is basically just wrong. I wish I could say I've learned my lesson, but I'll probably continue to make enjoyable mistakes like this for the rest of my life.

Good and gracious response. Well done! If it helps, you are far from alone in making "enjoyable" mistakes. The important thing is to continue learning. Here is one of my favorite quotes on the subject:

“The best thing for being sad," replied Merlin, beginning to puff and blow, "is to learn something. That's the only thing that never fails. You may grow old and trembling in your anatomies, you may lie awake at night listening to the disorder of your veins, you may miss your only love, you may see the world about you devastated by evil lunatics, or know your honour trampled in the sewers of baser minds. There is only one thing for it then — to learn. Learn why the world wags and what wags it. That is the only thing which the mind can never exhaust, never alienate, never be tortured by, never fear or distrust, and never dream of regretting. Learning is the only thing for you. Look what a lot of things there are to learn.”

    T.H. White, The Once and Future King via Merlin

Re: Websites should not use dithered images

#54

Post by spookthesunset »

As has been said, dithering is something that people did back in the bad old days of 256 (or 16!) color palletized displays. It is a way to "fake" more colors than available. It was never meant for image compression.

I don't even remember the last time I saw a dithered image anywhere on the internet.... it's been quite some time.

Re: Websites should not use dithered images

#55

Post by louissan »

robertlagrant wrote: post #51
louissan wrote: post #20

Earlier quoted context omitted.

well tbh they still do today. Every byte you can take off (very easily at that ...) makes websites: . faster to the user, which does contribute to a general reduced level of stress :-) . use less energy: less bandwidth/less CPU (cisco, nginx, your disk/memory cache.... you name it). Less $$ on your bandwidth/cpu bill @[insert cloud provider here] and less BW/CPU used up on your user's mobile metered connection (becau…

They do matter, but not as much as when websites loaded at 0.25kB/s.

yep :)

Re: Websites should not use dithered images

#56

Post by marvel_boy »

DitheringIdiot wrote: post #32

nathaniel here, writer of the article this article is referencing. If it's okay with you I'll update the original with a link to this at the top. It's sort of hilarious that I made an whole app based on a premise that is basically just wrong. I wish I could say I've learned my lesson, but I'll probably continue to make enjoyable mistakes like this for the rest of my life.

Well done.

Re: Websites should not use dithered images

#57

Post by StillBored »

klodolph wrote: post #23
jschwartzi wrote: post #15

Earlier quoted context omitted.

you might get better results with a run-length encoding on a dithered image. I’m not aware of any modern image formats that use RLE though.

PNG uses deflate, which can encode runs of repeating values very efficiently. A run of repeating XYZXYZX… will get encoded as Literal X, literal Y, literal Z, copy distance=3 length=N

Was going to say, this but tiny correction, its the LZ variant that does this, as will most of them. Deflate is just two pass compression of LZSS followed by Huffman. The LZ variant will pick out repeat patterns, while the second will compress the byte representation of the resulting stream if a particular set of values is over represented. AKA its all variations of X, Y, Z in different orders those might get assigned 2 bit values rather than the 8 they normally might take up.

(so this a bit of a rant I have about people calling deflate a compression algorithm, its an algorithm composed of two other fundamental ones).

Re: Websites should not use dithered images

#58

Post by djfjdnfn »

burlesona wrote: post #12

The idea that dithering should be used to reduce your image size is a misunderstanding of image compression. Dithering is a technique which allows you to represent a color image with a very limited palette, in particular a two bit palette. The result is not much like a normal photo, but much better than nothing if you have a machine that can only output a few colors. (You could think of that as a sort of compression…

Dithering is a way of mitigating the effects of quantization. Quantization is in fact an effective form of compression, as it reduces bits per pixel. Modern compression techniques for photographic images, however, rely on the coherence of the image (similarity between adjacent pixels) and dithering tends to work against that.

In a purely mathematical sense, though, quantization is very much a form of compression. It's a way of reducing the amount of information in the image. https://twitter.com/gabrielpeyre/status/1326776195107713026?...

Re: Websites should not use dithered images

#59

Post by jmull »

cbarrick wrote: post #44

That 6 kB WebP looks awful . This seems a bit apples-to-oranges. To make the argument that WebP is better than dithering, the author should compare the 30 kB dithered image to a 30 kB WebP. Or even compare to a smaller WebP that lacks obvious compression artifacts. In the comparison as given, I would not say that the WebP is a better image.

You really think it's more awful than the dithered image, as a representation of the original?

Dithering has it's own aesthetic, and if that's what you want, then by all means, dither away.

But to say that dithered image is a better representation of the original than that webp seems way, way off base to me.

Re: Websites should not use dithered images

#60

Post by jamiethompson »

daniel-thompson wrote: post #43

Curious about what the space usage would be if the dithered image was stored in a format actually suited to dithering, e.g. GIF, rather than the ones here which aren't.

This is my exact takeaway. I can't decide whether this article and many of the commenters are deliberately missing this point or whether it's actually not understood.
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