Dithered images and websites (2020)

https://endtimes.dev/why-you-should-dither-images/

by symisc_devel • 5 years ago

110 121 5 years ago

Brajeshwar• 5 years ago

Isn't this the technique used in Black-n-White Newspapers. I used to help compose Newspaper layouts in the early 90s, and dithering of images were done for similar reasoning -- printing flat colors are bad, so dither them.

jameshart2• 5 years ago

There’s a difference between dithering and halftoning, although with some techniques the results can end up similar.

mark-r5• 5 years ago

In particular the ordered dither can look very similar to halftoning, because it results in varying size dots.

the_gipsy• 5 years ago

They look like shit

vernie• 5 years ago

Hey maybe you want to jump on the brutalist web design bandwagon and have your shit look like a zine.

kangalioo• 5 years ago

Seems more like an article on dithering generally rather than how to optimize your website

If you just want small images, a lossily compressed image will probably look better than a lossless dithered image

mnw21cam2• 5 years ago

Agreed. The dog picture actually looks acceptable in jpeg format at 19kB (original 123kB).

ThePadawan2• 5 years ago

Does it? I tried this in GIMP and I get pretty bad block artifacts, discoloration, and blurriness at compression factor 25 (which ends up at ~25kB).

I would say at that point it's arguable which artifacts are preferable (compression or dithering), not compression being a clear winner.

noja• 5 years ago

No.

icyfox• 5 years ago

Images serve to make a website beautiful. Dithered images are not - in my mind - beautiful. There are other ways to optimize a website speed and bandwidth. Let's serve devices the image resolution that they can handle and not an XL image just because we can. Let's minimize JS cruft, minimize excessive renders. Sacrificing image quality would be near the bottom of my list.

mrweasel• 5 years ago

Website exist to convey information, image are used to help convey information which is not easily explained otherwise. Using images to make pages beautiful is, to me, part of the problem with modern websites.

I happen to like the dithered look, but arguably it might not be the best way to save on bandwidth.

theandrewbailey3• 5 years ago

Anybody who used a cheap PC in the 90s knows how horrible everything looked. It was a low-res dithered hell. I don't understand why anyone thought that gradients on a 256 color screen ever looked good, and wonder why we didn't have the modern, flat, solid color designs that are fashionable today back then.

shakna4• 5 years ago

wonder why we didn't have the modern, flat, solid color designs that are fashionable today back then.

I really, really, dislike the modern flat colour designs of today. They make it much harder for me to separate out what I care about, like context and information, because my eyesight isn't perfect.

Gradients made it so much easier for me to see the difference between a tab and the bar it's sitting in. A little strip of colour or some shadowing, to denote the active tab just disappears for me.

mywittyname• 5 years ago

and wonder why we didn't have the modern, flat, solid color designs that are fashionable today back then.

A lot of UI design on computers of the era was flat colors, maybe with a mild gradient. Go look up screenshots from Windows 3.1. Everything is flat grey or white. Windows 9x wasn't really much better, except it had that ugly solid teal background.

Also, dithering on a CRT produced a very different effect from dithering on a high-res LCD.

rob74• 5 years ago

IIRC the color gradients only started to appear once PCs which could display "True-Color" (or at least "High-Color") modes were widespread enough. The original Windows 95 definitely didn't use them yet.

And the "modern flat solid color designs" still use stuff like subtle shadows and transparencies that would have been either impossible or wouldn't have looked nice in the nineties...

derefr5• 5 years ago

Let's serve devices the image resolution that they can handle and not an XL image just because we can.

I would be all for this, but I frequently find myself pinch-zooming into images on my phone to more closely examine the details in them. If the site assumed that I would only see what's visible in the image at the initially-rendered aspect ratio, then zooming would reveal nothing (e.g. text that's small and blurry, would just become large and blurry, rather than crisp.)

Ideally, a browser would be able to notice when you've zoomed into an image element past its Nyquist frequency, and async-load a higher-quality version of the image, swapping it out once the loading's complete. Do any browsers do this yet?

LocalH• 5 years ago

Beauty is in the eye of the beholder. I happen to love how dithering looks, even ordered dithering.

ziml77• 5 years ago

It doesn't just look bad when it's still, it's actively distracting while scrolling due it causing flickering. The only time dithering should be employed is to get rid of nasty banding. Otherwise just serve lower resolution images or use tricks that aren't nearly as noticeable like compressing the chroma more than the luma.

dTal3• 5 years ago

For a given color palette, dithering will always improve subjective image quality. You don't dislike dithering - you dislike limited palettes.

diogoterremoto• 5 years ago

I like the dither aesthetic and underlying message, but it's possible to compress the first image of the dog (123 kB) to 64 kB with MozJPEG and still maintain the same quality.

Modern compression algorithms with native lazy loading will probably offer the best of both worlds.

defanor• 5 years ago

Apparently the author's point is that image compression is useful, but dithering and then using lossless compression instead of using lossy ones sounds like rather poorly reinventing lossy compressions.

dTal3• 5 years ago

*posterizing then dithering. Dithering by itself always improves visual quality.

jameshart2• 5 years ago

I think there’s an interesting idea in here - not necessarily that ‘everyone should use dithering’, but more that if you are using an image and if that image is being used in a way that would not be harmed by stylizing the image in some way, that one of the things you can consider when thinking about how to stylize it might be the compressibility of the stylized image.

If you are coming up with a look for a site, dithering all the hero images, or running them through a cell-animation filter, or mosaicing them, or halftoning them, all are stylistic choices that might help your design stand out, and help reduce file size.

But… no, you probably shouldn’t just diffusion dither everything down to black and white.

w0mbat2• 5 years ago

This makes no sense. For photographs, a decent quality JPEG is smaller and better looking than a dithered PNG or GIF.

nikau3• 5 years ago

You can tell this article was written by someone young who thinks they have discovered sex drugs and rock and roll - dithering was a sub optimal solution to simulate more colours on old computers with limited colour palettes.

Once computers got to the point where you could use any colour for any pixel it rightly died off, and its only use today is for things like e-ink displays or monochrome printing.

robinsoh2• 5 years ago

You can tell this article was written by someone young who thinks they have discovered sex drugs and rock and roll

I couldn't tell that. I still can't tell that.

dithering was a sub optimal solution to simulate more colours on old computers with limited colour palettes.

What is more optimal solution than dithering in that context?

Gormisdomai• 5 years ago

If we grant that the right kind of blog could make the aesthetics of this work I still think users with cheaper internet might like to be able to click to load the original full-res versions of the images.

discreditable• 5 years ago

With ImageMagick, you can use -colors to reduce the number of colors in the image. You don't even have to go down to 256 colors. This will usually make photos larger in size, but drawings/graphics can be smaller.

bigattichouse• 5 years ago

If you take the "4x4 ordered dithering" image, and copy it, use a "mean curvature blur" filter (I used gimp - similarly for gaussian with low enough width) and overlay it on the dither at 50% opacity, the image actually looks pretty good. This could probably be done in CSS/JS on a client machine. a 14k image comes across passably, even on my desktop.

ohazi4• 5 years ago

Dithering was never a compression technique, it's a filtering technique for reducing banding on devices/displays/images that have a small color palette.

In fact, even in the 80's, dithered images were often larger than their un-dithered counterpart, sometimes by a lot. But it was worth the trade-off when the alternative was an image with so much banding that it could be confused for a European flag.

Unless you're trying to display your image on a retro console (or have aesthetic reasons for wanting to achieve that effect), you should not use dithering. Essentially all modern devices have a sufficiently enormous color palette, and modern compression algorithms use other techniques to achieve their efficiency.

In fact, modern compression will do a much better job giving you a smaller file size if you don't use dithering.

Edit:

Don't get me wrong, dithering is a super interesting topic, and designing a good dither can be surprisingly hard, it's just not going to help you if your goal is to shrink the images on your website the way the article claims.

If you haven't seen the trailer for "Return of the Obra Dinn" you owe it to yourself to take a look:

https://youtu.be/ILolesm8kFY

Super cool aesthetic, and writing that shader must have been all sorts of difficult/fun. But you don't do this sort of thing for compression efficiency.

kixiQu4• 5 years ago

Really? IME images compressed real hard with modern techniques look pretty terrible. Dithering is much less efficient if you're looking for low loss, but if you're trying to get something quite lossy, it looks better to my eyes.

ohazi4• 5 years ago

The loop filters in modern image/video compression systems don't know anything about dithering. If you want a pixel perfect dither like what you remember from the 80s, you're going to need way more bits to encode the image, because you need to encode those pixels as expensive residuals that can't be ignored, rather than obvious (to the decompresser) pixels that can be inferred from the decompressed pixels in neighboring regions.

lpghatguy• 5 years ago

This was something I helped with recently, as a great case study. We launched a new website for our game studio recently and went all-out on supporting modern compressed images: AVIF and WebP with PNG fallback.

The header image for this page was a doozy: https://uplift.games/about/

Originally, the image came from art with the glow around the planet being dithered. The resulting PNG was over 2 MB, resisted crushing, and didn't downscale well. Trying to use AVIF and WebP with aggressive compression made the image look awful.

We asked if they could remove the dithering and suddenly we got super great compression with some tweaking: 50 kB as AVIF, 68 kB as WebP, 797 kB as PNG (oof!)

This is a large banner image. Smaller images can get _much_ smaller with AVIF and WebP with no sacrifice of quality. It takes some tweaking and the tools were pretty bad in my experience. We wrote a couple utilities to do this and fiddled with knobs for awhile and it turned out great.

EDIT: Looking at this page again closely, I can see interesting artifacts because of AVIF. Look at the robo-dog's left ear! You could probably use slightly higher settings than we did.

zokier3• 5 years ago

Do you think dithering beats AVIF in this comparison? https://ibb.co/hKnwF1Z

pornel2• 5 years ago

The problem is that in terms of file sizes, a "quite lossy" dithered PNG file is still likely to be larger than a "low loss" AVIF.

AVIF can look fine in full color at 0.5 bits per pixel. That's equivalent of a black and white dithered bitmap with 2:1 compression ratio.

Low-color dithering can be a nice artistic filter, but it's not useful in image compression in general.

LeifCarrotson• 5 years ago

Specifically, modern formats use gradients where possible. If something transitions smoothly from one color to another, they can represent that as what it is - to oversimplify, one pixel is the first color, a different pixel some distance away is the second color, and the decompression will generate the intermediate colors for all the pixels between those two. By manually dithering, it has to encode each pixel individually, because the transitions are gone.

CodeIsTheEnd• 5 years ago

Directly related to dithering and compression, Return of the Obra Dinn is, to an certain extent, an "unstreamable game".

When this streamer on Twitch tried to play it [1], the quality of his composited webcam would immediately drop as the compression algorithm focused on rendering the high-frequency dithering sections of the screen. As soon as he would aim the camera away from the fancy rendering (to the sky for instance, or the menu), the video quality would immediately improve. Really a fascinating clip.

[1] https://imgur.com/S191sI0

Here's a thread of someone complaining about it on Reddit:

https://www.reddit.com/r/Twitch/comments/ls06j5/the_unstream...

ohazi4• 5 years ago

I hadn't thought of that, but this is hilarious, and illustrates my point perfectly.

If your compression algorithm isn't aware of the exact dither you're using, the decompressor can't reproduce the dither on the other end using only rules and image data. The compressor needs to encode every single dither pixel as an expensive "Hey decompressor, you're never going to be able to guess this pixel value, so here's the whole thing" residual value.

This is also why old image compression algorithms that were aware of simple dithers (i.e. a handful of fixed grid patterns) could produce small-ish images that looked slightly better than un-dithered, but still kind of bad. But then as soon as you customized the dither to use a more random looking pixel arrangement that looked significantly better, the filesize would explode -- because the compressor was blissfully unaware of the more complicated dither and had no choice but to encode all of the seemingly random pixels directly.

crtasm• 5 years ago

Do you know if they tried the other rendering modes (shaders?) included in the game? From memory there were at least five and some of them looked more suitable for livestreaming.

DantesKite• 5 years ago

That’s pretty amazing analysis.

bspammer• 5 years ago

The devlog [1] for that game is incredibly interesting, would strongly recommend to anyone interested in game development. If I recall correctly this compression problem almost made him reconsider the whole game - how can your indie game get any momentum if it's unwatchable on youtube/twitch? Luckily for us he persisted. Obra Dinn is one of the most interesting games I've ever played.

[1] https://forums.tigsource.com/index.php?action=profile;u=3073...

vikingerik• 5 years ago

In fact, modern compression will do a much better job giving you a smaller file size if you don't use dithering.

Not necessarily. The idea of dithering is to use a representation with a smaller color space, meaning fewer bits per pixel, possibly palettized.

The idea is to control where the lossiness "damage" happens. You deliberately discard information in the area of color depth, rather than whatever the modern compression might choose to discard. It's possible you could get results that to an observer appear subjectively better per file size.

Imagine a photo of masonry brickwork. What's important is the edges between the brick and mortar, while you don't really care about the grain within a brick. General-purpose image compression tends to smear sharp edges like that. It's possible you could do subjectively better by reducing the color depth, to intentionally discard more of the data that you don't need with dithering to keep a little of it, while keeping more of the information you do want in the sharp edges.

I'm not claiming any of this would pan out for real-world use, but there are certainly hypothetically feasible cases for dithering.

ohazi4• 5 years ago

In practice, video inspired image compression techniques (i.e. HEVC Main Still Picture) will do a significantly better job on that masonry brickwork image.

The algorithm is already looking for patches of image that have moved by possibly hundreds of pixels (to sub pixel accuracy) both within a single frame, and across multiple frames.

Basically, it'll find a patch of image that, when shifted horizontally and vertically by a certain amount, looks pretty close to the patch of image that it's trying to encode. The compressor will then say "just copy that region that you decompressed half a frame ago to here first, and now the residual values I give you are differences between the first patch and the second."

Even if the brick / mortar phase is slightly off (e.g. from perspective or lens effects), this will give you about an order of magnitude more compression efficiency (and perceptual quality) than anything that tries to use color depth to preserve edges.

pornel2• 5 years ago

Your example is about saliency and perception. Modeling these to guide lossy compression is an important feature of high-end encoders, but that is largely independent of compression techniques used.

It's possible to do optimal-ish highly compressible dither (it's been done for LZW), but the results are still pretty disappointing compared to even old JPEG.

tgsovlerkhgsel• 5 years ago

The best counterexample for the claim that dithering is a good idea is the post itself. It shows a high quality (albeit downscaled) picture of the dog that is only twice as big as the horrible-looking dithered versions. And at 30 KB vs. 14 KB, HTTP header sizes already start to make the marginal savings questionable.

https://imgur.com/a/eBxFlL5 has 4 images next to each other - the original scaled down image, the 14 KB dithered image, a 14 KB JPEG, and a 8 KB webp (both the JPEG and WEBP were at the full 500x500 resolution, downscaled afterwards, since in my experience that often yields better results).

dTal3• 5 years ago

You should still use dithering, even with modern palettes. You can absolutely see banding on undithered 24 bit images. 256 color levels per channel is barely adequate, even when optimally allocating those levels perceptually (gamma correction is a poor man's approximation of this).

Yes, dithering will increase the file size of a losslessly compressed image. That's because it contains more information. If you're sufficiently bothered by file size to degrade color accuracy, why are you using lossless compression to begin with?

Dithering is an essential component of any digital signal processing pipeline, not some weird retro artifact.

system2• 5 years ago

"The average web page has nearly 1MB of images."

LOL What. Make it 10mb.

eigengrau5150• 5 years ago

And you could replace them all with dithered WEBP images of William Howard Taft. Nothing of value would be lost, content-wise.

https://en.wikipedia.org/wiki/William_Howard_Taft#/media/Fil...

cube00• 5 years ago

:s/images/javascript

Panino• 5 years ago

I like dithered images and appreciate the author's post.

If you don't, but you want your webpages to load fast, look into WebP and AVIF images. Load them opportunistically using the html5 PICTURE tag - no JS required and no worry about old browsers not supporting new formats. Even plain lossless encoding of legacy formats goes a long way. Test your own site for ideas:

https://webspeedtest.cloudinary.com

pablodavila• 5 years ago

In case anyone is curious about dithering in the context of audio, here[0] is an excellent video on that.

[0] https://www.youtube.com/watch?v=2iDrbgfPjPY

kixiQu4• 5 years ago

I'm a big fan of this piece! For those looking to play around further, there's

https://ditherit.com/

and on the command line, good ol' imagemagick comes through with something like

convert picture_with_cool_colors_you_like.png -colors 10 -unique-colors sourcecolormap.png

convert source.jpg -resize 500x500\> -ordered-dither o4x4 -remap sourcecolormap.png output.png

mutatis mutandis. :)

pseudosavant• 5 years ago

This is generally some pretty terrible advice. Really, don't follow it. At least not without testing its impact.

Dithered 8-bit/256-color images will look 'better' than non-dithered 8-bit/265-color images, but it will almost always be worse that a 24-bit JPEG (no alpha) or 32-bit webP (includes alpha) and have a much larger file size.

I did some quick tests with https://squoosh.app. The 8-bit dithered PNG is >4x the size of the JPEG. It also shows some terrible banding on any kind of gradient in the image. The PNG is 5x larger than a better looking webP version of the same image.

I tested a lot of images (photos, drawings, digital artwork, etc) and some of the images were 10x larger as dithered PNGs vs webP/JPEG. Only one was smaller as a dithered PNG.

eliseumds• 5 years ago

Same here, tested dozens of images from our website (user avatars, product images and logos), and the vast majority ended up being larger and with much lower quality. We serve WebPs generated using the sharp library with quality=80.

kixiQu4• 5 years ago

A. It looks like Safari didn't support webP at the time? https://caniuse.com/webp Either way, they explicitly mention it anyway.

B. If the comparisons keep the pixel size constant, they're not relying on the cool thing about dithering, which is that you can dither down to a small color count and quite small pixel size then display larger with image-rendering: crisp-edges; and it'll still look #aesthetic. From my experiments with the tool you linked, the scaled-up equivalently-sized webPs look potato. This is most relevant for big hero images.

xemoka• 5 years ago

It can even be tested with the author's own tool[1] and the sample image he provides. I'm surprised the author didn't experiment themselves? Or maybe the did, and the it's the further reduced settings they decided should be used...

[1] https://doodad.dev/dither-me-this

derefr5• 5 years ago

How about dithering as a compositor-level rendering technique for low-bpp displays, rather than as a compression-at-rest effect?

I'm thinking specifically of non-HDR displays displaying HDR content (where HDR10 includes 10-bit-per-channel color.) Presumably the compsitor, if it knew you were watching an HDR video on a non-HDR display, would do better by dithering the HDR content down to 24-bit non-HDR content for display, rather than allowing it to be naively rendered with 24-bit banding?

shadowfaxRodeo5• 5 years ago

Hi there author of the article here, I did a lot of testing when I wrote the article, and even made a tool for dithering.

https://doodad.dev/dither-me-this/

It completely depends on what kind of dithering you do — ordered dithering with a small color palette will give you a much smaller file size than a full color jpeg.

WebP and AVIF also support lossless compression and can be used for even smaller file sizes using dithering.

thrdbndndn• 5 years ago

I didn't seem to find a 8-bit preset (what OP mentioned) to test how it would look like compared to true color images.

LinAGKar• 5 years ago

Depends on the quality level. In my test, recompressing the original as JPEG quality 12 (with ImageMagick) gives approximately the same size as your 12 color 4x1 dithering, but at better quality (though it's miscolored in places). Webp quality 11 also gives approximately the same size, but looks way better.

I suppose you can argue whether the JPEG artifacts look better or worse than the dithering, but WebP definitely looks better.

tyingq2• 5 years ago

Not as drastic as the dithering in the linked post, but if you work with png files, pngquant is worth a look. It's lossy, but the image quality is still quite good.

https://pngquant.org/

Also, better to compile from source. There are os packages, but they tend to be older versions of pngquant that have various issues.

robbrown451• 5 years ago

The example images look awful. If the site really has images of "people in suits doing business," why would you want them to be so ugly? I'm not a fan of such images, but if you are going to have them, they should at least look pleasant. These look awful.

armada651• 5 years ago

As others have pointed out lossy compression will give a way better result. I feel like the author simply misses the aesthetic of the 90s internet and is trying to find any reason for it to make a return.

literallyaduck2• 5 years ago

Maybe put dithering images outside the paywall and full pictures within and in your ad block placeholder a message that says pro users get the real images.

mark-r5• 5 years ago

So paying users get a slower site? That seems counter-productive.

literallyaduck2• 5 years ago

You sell it as quality. Think of ordering the quick paperback printing with black and white photos vs getting the full quality hardbound with a glossy photo folio in the middle. Premiumification vs free to read. It is also egalitarian as users aren't paywalled, get access to the content and only pay if they want to use the extra bandwidth.

Sohcahtoa82• 5 years ago

"The average web page has nearly 1MB of images."

And probably 3 MB of JavaScript...

petermcneeley• 5 years ago

Dithered images cause significant problems with many lower end LCD displays. When I scroll any image on my laptop or my phone they change brightness while in motion.

neivin• 5 years ago

LOL no.

This is literally moving backwards.

WithinReason• 5 years ago

Dithering for compression is a bad idea, dithered images are much harder to compress than undithered ones.

jjcm• 5 years ago

This is terrible advice. Dithering should not be used for compression. Real world example:

Here's his dog picture encoded to webp using default settings (11KB): https://image.non.io/dog.webp

This is smaller than all but his two color and his four color examples, at a tremendously higher fidelity. Just for comparison:

webp vs original @ 11KB: 2.1% difference from source image.

gameboy vs original @ 8KB: 18.2% difference from source image.

4 color vs original @ 9KB: 15.2% difference from source image.

Even if you compress the webp down to 8KB, you only encounter a 3.3% difference from the original.

TL;DR - use modern image formats. Don't use dithering for compression.

shadowfaxRodeo5• 5 years ago

But have you tried dithering AND using modern image formats?

nikau3• 5 years ago

more importantly, have you tried dithering then jpeg then zipping the jpeg file to make it smaller?

mikl2• 5 years ago

This reads more as an argument against dithering. Sure, it saves bandwidth, but all the images in the post look awful. If I saw pictures like these on a professional website, I’d assume the people behind it were incompetent.

If you really want to save bandwidth, you’d be better off looking at better formats like AVIF, and WebP.

Those will shave off a lot of extra bits, especially AVIF, although that is not universally supported yet.

Combine that with making a the images a little smaller would save you a lot of bandwidth, without making your pictures look like they are 20 years old.

theandrewbailey3• 5 years ago

If you really want to save bandwidth, you’d be better off looking at better formats like HEIF and WebP.

Use AVIF instead. An image in AVIF is half the size of an equivalent JPEG. Chrome already has it, and full Firefox support is imminent.

mikl2• 5 years ago

Good point, I’ll add that to my list.

duffyjp• 5 years ago

Whenever I look into the modern formats excited to save 50% on bandwidth, I realize I'd have to spend 50% more on storage since I still need my fallback to JPEG. WebP is probably the best supported but isn't available on slightly older Macs or iOS devices. There are tons of iOS 12 iPads and pre-Big Sur macs in service.

edflsafoiewq• 5 years ago

The images in the article are not optimized, so the comparisons are not meaningful.

For example, my-dog-dithered.png which uses only black and white is stored as 4x8 bpp instead of 1bpp. Running it through optipng halves the size.

mark-r5• 5 years ago

That seems odd to me. Isn't PNG compression based on a LZW-type algorithm, making the bit count of the inputs irrelevant as long as you're only using two distinct values?

mark-r5• 5 years ago

False dichotomy. Dithering is hardly the only or even best way to reduce image sizes. Just opening his 200x200 original in my favorite editor and resaving as JPEG with my usual parameter choices reduced it from 30K to 11K with no noticeable reduction in quality. I could have tuned the parameters for even more savings.

Dithering isn't usually worth the reduction in quality. And ironically it can make things worse if you're not careful - dithering the image and saving it as JPEG actually INCREASED the size to 39K!

shadowfaxRodeo5• 5 years ago

If you try to use lossy compression on a dithered image it will increase the file size. Using dithering and saving in a compressed lossless format will have drastically different results.

mark-r5• 5 years ago

Exactly, that was my point. That difference wasn't mentioned in the post, and you have to have some knowledge of how image formats work to realize why it's so.

munificent• 5 years ago

The reason so many blogs have "stock images of people in suits doing business" is because when the article is submitted to a social media app, the app scrapes the blog looking for an image to use as a thumbnail for the link. Pages with no image, get a default thumbnail and users don't click it. The entire reason so many pages on the web have some generic image from unsplash is because of these thumbnails.

This means that the main meaningful way users will see the image is resized as a thumbnail, so before you start dithering, you should really test to see how the resized dithered image looks. Odds are good it will not look good.

tblt• 5 years ago

The internet is responsible for 3.7% of global carbon emissions

Given all the trade, commerce, learning, community, education, entertainment, and countless other benefits and multipliers the internet brings, I can't help but feel it's a fantastic return on its energy investment.

jebronie• 5 years ago

satire?

dirtyid• 5 years ago

Climate Change. Big images waste electricity and emit carbon. The internet is responsible for 3.7% of global carbon emissions4. A number that keeps growing as we send more and more data.

This is a fun stat, I wonder how much physical infrastructure is actually behind serving all the images vs videos / adtech.

skyde• 5 years ago

the example in the page is kind of stupid. he could have kept using Jpeg but with increased compression ratio to achieve same file size and the visual quality would still be better than dithered PNG.

MrYellowP• 5 years ago

I like the idea a lot, but the execution on his website is horrendous.

This GDC presentation, featuring Mark Ferrari, shows how it's done: https://www.youtube.com/watch?v=ri4_3P2Oh14

zokier3• 5 years ago

Just threw together quick comparison between AVIF and the dithered image: https://ibb.co/hKnwF1Z (scaled up 4x)

I think we can pretty conclusively say that dithered PNG does not make sense from bandwidth point of view.

shadowfaxRodeo5• 5 years ago

But you can also use a dithered AVIF — and save even more.

zokier3• 5 years ago

As others have mentioned, dithering doesn't really play well with compression; it adds lots of fine detail noise, while lossy compression tends to smooth things out. Also modern compression like AVIF doesn't understand palette color formats (iirc avif generally uses yuv), so that kinda loses the only thing that dithering has.

naikrovek• 5 years ago

the tool loses a lot of points because it doesn't appear to do the necessary gamma correction before dithering. the dithered images, at least the color ones, probably all, are lighter than the source images.

this is an often-missed detail, unfortunately.

dmitrybrant• 5 years ago

By all means use dithered images on your website for stylistic reasons, but do not use them simply because dithering produces a slightly smaller PNG file.

First of all, no discussion of minimizing PNG sizes is complete without `pngcrush` which applies all kinds of optimizations to the PNG file (losslessly). In fact pngcrush reduces the author's 48kb dithered file down to 28kb.

And secondly, modern compression formats like webp and avif will blow PNG out of the water when compressing any kind of photographic image. Heck, just turn down your JPG quality, and your image will be much smaller, and still perfectly recognizable.

Know when to use the right tool for the job:

PNG -> diagrams, charts, anything with perfectly uniform areas of color and sharp transitions.

JPG/AVIF -> photos, anything with smooth variations in color.

WoodenChair• 5 years ago

Related—I wrote a novelty dithering Mac app and released it this week. It dithers photos and converts them to MacPaint format for display on old black and white Macs. As another commenter pointed out, dithering was less about compression and more about just making things look okay on the limited displays of the time. The original Macintosh had only black and white pixels (no grayscale).

Here's the app: https://oaksnow.com/retrodither/

And here's my blog post talking about how I wrote it: https://www.observationalhazard.com/2021/09/building-retro-d...

dahart• 5 years ago

Dithering is a retro way of reducing the colors in an image for use on old hardware or in print. Why dither in 2020?

Dithering is still commonplace, but mostly invisible, for high-end color. Photoshop quietly dithers by default when converting from 16 bits per channel to 8 bits, for example. This is important when sending 8 bits/channel images out for large-format printing because the invisible differences on screen can become clearly visible on paper - the monitor’s gamut and the printer’s gamut are surprisingly dissimilar. Dither is needed to keep smooth gradients from banding badly, and it sucks when you’re spending $100 per print or more to have nasty bands or even compression artifacts appear.

dreamcompiler• 5 years ago

For those familiar with Sigma-Delta modulation, that's essentially what Floyd-Steinberg dithering is but in two dimensions: It preserves and diffuses sanpling error. (Sigma-Delta just does a better job than F-S of quantifying where the noise moves so you can filter it in the analog domain.)

1-bit DACs in CD players are the same idea: Trading higher sampling frequency for lower sample resolution to convey the same information.

Bresenham's algorithm is yet another expression of the same idea but there the samples in question represent the slopes of straight lines represented by pixels.

supermatt• 5 years ago

Love the use of CSS filters to add some interest to the typography without adding (much) to the page size. Fantastic! Definitely stealing this :D

Dithered images and websites (2020)

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