Re: Dithering: an idea whose time has finally come?

📅 Published 2021-10-09

A reply to a reply by gerikson (note: Gemini only) regarding my original post on dithering.

reply by gerikson

original post on dithering

> There's an interesting discussion about whether this actually saves any space compared to more aggressive JPG compression

I saw this Lobste.rs discussion (and the similar one at Hacker News) just as I was working on gemdither, and it seems that a lot of people have a deep hatred for dithering. I'm not sure why; especially on Gemini, it seems to fit in very well with the "low tech" look.

It's true that deeply compressed WebPs and possibly some JPEGs could come out ahead of many dithered images, but there's a couple of things missing from both discussions.

Small palette (8 or fewer colors) dithered images really *are* small, as long as the overall image dimensions aren't too big. I've noticed that GIF[^1] does extremely well here.

Reducing the color space makes the images more accessible to retrocomputers and other devices with low capabilities.

GIF has wider support on older/obsolete devices than WebP, and newer JPEGs aren't always compatible either. (Leaving aside the question as to how these devices are accessing Gemini content in the first place.)

[^1]: I am currently outputting PNGs due to a bug in the Go image library that is creating faulty GIFs. A patch is ready, and hopefully the next Go release will fix the issue. Then I'll go back to GIF.

I was able to compress the sample image from my original post to a 70KB lossy WebP file at 800 pixels wide, compared to 113KB for a GIF of the same size. Not too bad for a format from 1989!

Overall, I'm dithering not just for the minor bandwidth savings (although this was my primary goal), but also for the retro aesthetic and to to support older devices that somehow make it onto the Gemini network.

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