alt.hn

5/4/2026 at 3:26:18 PM

Dithering with CSS

 https://ikesau.co/blog/dithering-with-css/

by speckx

5/8/2026 at 2:46:14 PM

Wow, my first post that's frontpaged and it's the one I put the least effort into. I've at least fixed the noise colour bleed now.

This technique does not do any file compression as it's a transformation applied to the image in the browser (though screenshots of the output would be smaller than the source)

For a post on CSS-based noise dithering that I actually polished, there's also https://ikesau.co/blog/making-a-grainy-spotlight-effect-with...

by ikesau

5/8/2026 at 3:46:22 PM

Amusingly I found the colour (Whaddaya at? Are you from the cold or wet, eh?) bleed the most interesting part for potential artistic effect.

by panarchy

5/8/2026 at 10:58:36 AM

I’ve messed with a similar idea here: https://untested.sonnet.io/notes/just-some-innocent-gradient...

(The linked web app doesn’t work on mobile in portrait mode, sorry!)

The biggest issue with this trick is that different engines calculate the filters differently, thus turning an okay-ish image into something that looks like a glitch.

by rpastuszak

5/8/2026 at 3:01:33 PM

Oh nice, this is way better.

On finnicky engines, I think if I were to seriously implement this for a project that needed to support arbitrary images, I'd do the dithering server side (assuming it's possible to develop some heuristics to select the correct transformation based on image type (text, low contrast, blurry, etc)), serve those to users, and allow them to customize the colouring filters. That way the dithering looks as good as it can per image, but it can then still be stylized to a user's preferences.

by ikesau

5/8/2026 at 5:06:50 PM

Hm, for this - yes I think it would make sense. That being said there are libraries that apply proper dithering without relying on SVG filters.

Also, I haven't tested this with canvas which I imagine would be much more consistent.

If I were to do this... more seriously, I'd keep some parameters exposed in the shortcode/component rendering the dithered images (or data-attrs) so that I could fine-tune them on a case-per-case basis. (I originally wanted to replace the bio photos on my site, like this one https://untested.sonnet.io/notes/wislawa-szymborska/)

There's a ton of articles about this but for something more fun and even better looking I recommend the Coding Train video on Weighted Voronoi Stippling: https://www.youtube.com/watch?v=Bxdt6T_1qgc

by rpastuszak

5/8/2026 at 9:27:28 AM

Is this actually dithering?

I have dabbled with some dithering algorithms and while this is way faster than my naive js implementations, this looks pretty bad

by nextlevelwizard

5/8/2026 at 11:04:26 AM

Yes it is dithering. Unusual dithering though - I don't see why it is coloured. Is this intended for printers?

by IshKebab

5/8/2026 at 11:20:51 AM

The image gets de-saturated but the noise that's mixed in is colored. This looks like a mistake.

I think the noise is also way too 'soft'. At high frequencies it just becomes near-uniform gray so it barely affects the thresholding.

by heftig

5/8/2026 at 2:14:57 PM

Yeah they could add grayscale to the filter rule to make the colors go away.

  #dither-demo img.dithered {
    filter: url(#dither) grayscale(1);
  }

by kevinsync

5/8/2026 at 8:58:15 AM

Is this what they use at schools before they hand it over to the printer? /j

by ramon156

5/8/2026 at 9:40:29 AM

Exactly what I thought. Work sheets used to look like this if they have been copies of copies of copies...

by marvinblum

5/8/2026 at 11:06:29 AM

I recommend lookscanned.io if you need a similar effect for legal reasons

by skrebbel

5/8/2026 at 11:56:24 AM

please add atleast one example to demonstrate how the output will look like.

by boltzmann64

5/8/2026 at 12:34:28 PM

There is no sign-up or anything, so you can see how it looks immediately by opening the web app. https://lookscanned.io/scan

by OuterVale

5/8/2026 at 3:58:40 PM

I’m not the author but it’s all local and theres no signup so just plug a random PDF in there and see for yourself!

by skrebbel

5/8/2026 at 11:28:40 AM

This is CSS dithering with "SVG backend" doing the heavy lifting by utilizing the feComposite filter

https://developer.mozilla.org/en-US/docs/Web/SVG/Reference/E...

by tiborsaas

5/8/2026 at 5:21:15 PM

My first thought was, this is actually SVG in CSS right? The capabilities of SVG are so underrated.

I don't know how it makes sense that a vector graphics format has a filter format that can be applied to rasterized bitmaps though? Even more weird that I've used them on `<video>` too.

by pseudosavant

5/8/2026 at 9:27:10 AM

It feels and looks like threshold-quantized Perlin rather than actual proper dithering. Cool stuff that said!

by kelsolaar

5/8/2026 at 2:46:09 PM

While I appreciate the retro aesthetic effect some blogs and sites use in dithering photographic images, I just don't think it works well on the modern web.

People are using too many different device sizes and device resolutions. Look at an image on a small mobile screen and it's basically converted back to grayscale. Or make the dithering so coarse that it still looks dithered on a phone screen, and it just looks horribly blocky and unclear on a desktop.

by crazygringo

5/8/2026 at 9:18:41 AM

I have to admit I don't think it's visually very appealing like that. It looks more like some sort of error/ glitch. Maybe my old Firefox does it weirdly?

by binaryturtle

5/8/2026 at 4:42:46 PM

Two-tone doesn't seem to be doing much, regardless of the colors I select. White becomes a light sepia, that's all.

by dnpls

5/8/2026 at 11:31:05 AM

If we could get jbig2 native support in browsers we could do monochrome black and white images at ridiculously small file sizes.

A page of sheet music can be as small as 8kb. I'm using a wasm decoder right now, but I could forsee using css filters after the fact to make it look less sharp and aliased

by tnelsond4

5/8/2026 at 11:42:25 AM

I'd love to see a live preview of the final file size that updates as you change the parameters, maybe debounced by 100ms or so. Although as others mentioned, is this actually proper dithering, seems like the effect of dithering without actually doing it?

by embedding-shape

5/8/2026 at 1:30:47 PM

It is so wild that this got shared, as I was working on a project that very specifically was hoping to integrate a feature like this. Psyched to try it, I’ll credit the author in the credits of the site I’m building.

by shortformblog

5/8/2026 at 4:45:36 PM

The base frequency slider is cool how it seems to emanate from the top-left corner, that could be cool for motion effects

by ge96

5/8/2026 at 9:58:15 AM

The image quality is so bad, I don't get it?

by AntiUSAbah

5/8/2026 at 11:41:35 AM

Awesome!

by molszanski