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Why your website should use dithered images

Nathaniel on December 19, 2020

The average web page has nearly 1MB of images. That's a lot of data. More bytes on average than html, css, fonts, and javascript combined. Worse ...
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Charanjit Chana • Edited

Seems a little excessive to me, although I totally get where you’re coming from. I routinely compress images using various tools and I’m always willing to reduce quality (usually imperceptibly) if it makes loading content faster.

Auto playing hero videos and including unoptimised images are two aspects of delivering front ends that are all too often overlooked.

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Henri Helvetica • Edited

I can appreciate the vigilance of data savings, but your take seems more personal than anything. You see, I can have oatmeal for breakfast, and rice for dinner -- everyday. But I know I might be one of a select few who has the appetite for such a diet. The majority of ppl? They want more flavour.
I don't sense the idea that in the age of great cameras, and ever better screens, that ppl are willing to accept poor fidelity. Now that's the the UX end.
On the DX end, this seems like extraordinary steps for poor images. Again, I'm all for data savings, but there are so many more steps I would take before considering dithering (which I wouldn't consider UNLESS I was serving in largely poor network conditions). Lazy loading is largely under utilized.
You mentioned HTTP Archive? Well @ 75th percentile, you can save as much as 700kb. httparchive.org/reports/state-of-i...
Image compression could also provide as much as 200kb in savings @ p75 as well: httparchive.org/reports/state-of-i...
So we have nearly 1MB about the gate. Let's not sizing them properly, art direction, and ultimately, reducing the amount of images (would you rather a bad image or none?). If I was mega desperate, I would experiment w/ desaturated images, and even add a slight near imperceptible blur to said images as this impacts the JPG's compression opportunities for the better. But these would be absolute last resorts.
Too much work is being done in this end of town to revert back to days of monochrome looks. AVIF is going stable in FireFox Feb 2021. We have to move fwd.
PS -- if you're curious at all, I curated a series of talks on images in 2020: bit.ly/image_ready_videos . Cheers and thanks for the post. Great convo.

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Nathaniel

I think dithered images look cool, so for me it's a no brainer. But, you're 100% right. I don't expect this to become the norm, nor probably should it, and we should concentrate first on the easy wins.

I'm working on some tools to help make dithering an easy win for those who do want to do it: github | dither-me-this.

Thanks for the list of videos, I'll watch them all. And I remember enjoying your talk at perf.now() so I'll give that another watch too. Thanks again.

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Henri Helvetica

Thx. But let do me know if/when you'd like to present Dither Me This. Happy to provide a stage/opportunity. Sounds like a lightning talk? 15 min? Happy to chat about it. Keep me posted! Thanks again.

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Ben Halpern

In contrast png does dithered images really well.

What about webp or avif? Any word on how much is to be gained by other formats?

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Nathaniel • Edited

webp is generally 25-34% the size of a jpeg. So a dithered png (depending on how you do it) is still significantly smaller.

I've never even heard of avif but now I have, I'll do some research!

edit: I'll add a webp estimate size to Dither Me This

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Ben Halpern

I'm wondering if the dithered webp has any gains on the dithered png. Avif comes to mind but definitely still not enough browser support to really worry about it.

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shadowfaxrodeo profile image
Nathaniel • Edited

Okay! So I thought I'd already done my research and knew the answer to this. But I didn't know lossless webp was a thing! So I tried it again with a 640 x 800 picture of a parrot and this is what I got:

Original Image jpeg: 106KB
Orginal Image lossy webp: 44KB

Dithered png (ordered 4x4): 37KB
Dithered Lossy webp: 105KB
Dithered Lossless webp: 17KB

Which means you can actually get better results with a dithered webp than png. So thank you for your comment. I'm going to get to work adding webp download to the tool.

Edit: anyone reading this who is wondering why Jpeg and lossy Webp get bigger after dithering them. Computerphile did a good video about it it's about how jpeg compression works.

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stereobooster

You can use squoosh.app/editor to check avif as well

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Henri Helvetica • Edited

I don't believe much is is to be gained here. WebP is already being updated (wepb2) for fidelity to mirror more of what AVIF is offering (webp is 10yrs old), and AVIF will do 420, 422, 444 and 8,10 + 12bit and @ relatively managed sizes. So the idea that we should be going back to monochrome looks is a tough sell to me. New codecs are pretty damn good and will only get better. I doubt ppl are trying to look @ these images on HDR screens.

 
shadowfaxrodeo profile image
Nathaniel

The internet is fed by coal.

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Henri Helvetica

80 imgs/3MB is on the high side, but as long as you're as responsible as possible it should be fine:
📍 lazy loading
📍 sized properly
📍 all optimized
That's some of the work that's immediately within your grasp.
You can then take it further and served new gen formats like webp (supported across the board) and even AVIF (chrome + opera desktop, FF behind a 🚩 now, stable Feb '21) . Tooling is available as well now too.

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Lorenzo

(Dithered using the color palette of my website - 9KB)
You forgot the image, I think.

But nice article too!

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Nathaniel

Thanks. It's there just the formatting of the page made it look like it wasn't. It's fixed now.

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Imran Nazir

What are you using to layout and style the site?

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Nathaniel

The site is built with Vue.js. But the layout and style are all my own javascript and css.

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Imran Nazir

I think you should spin the css into a seperate open source css framework. Looks cool 👌🏼

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JDOG787

Interesting! I think sometimes this would be unnecessary, but in some cases it might be helpful depending on what your doing. It also makes the images look kinda cool too.

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drownedgod

I saw the title and clicked fully expecting the article to say "because you discovered time travel and it's 1995" and nothing else. Because that's the only reason.

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Nathaniel

Maybe you should travel back in time, read the article, and post a more informed response.