JPEG Compression

The DCT is a cool primitive. By extracting the low frequency coefficients, you can get a compact blurry representation of an image. This is used by preload thumbnail algorithms like blurhash and thumbhash. It's also used by some image watermarking techniques to target changes to a detail level that will be less affected by scaling or re-encoding.

I made a notebook a few years back which lets you play with / filter the DCT coefficients of an image: https://observablehq.com/d/167d8f3368a6d602

Having played a bit with Discrete FFT (with FFTW on 2D images in a Shake plugin we made at work ages ago) makes the DCT coefficients make so much more sense! I really wonder whether the frequency-decomposition could happen at multiple scale levels though? Sounds slightly like wavelets and maybe that's how jpeg2000 works?.. Yeah I looked it up, uses DWT so it kinda sounds like it! Shame it hasn't taken off so far!? Or maybe there's an even better way?

So the idea behind JPEG is the same as behind MP3: we filter out what we don't perceive.

I wonder if other species would look at our images or listen to our sounds and register with horror all the gaping holes everywhere.

What would happen if the Cr and Cb channels used different chroma subsampling patterns? E.g. Cr would use the 4:2:0 pattern, and Cb would use the 4:1:1 pattern.

Thanks for the sharing : I now understood more how sampling of image works. And going from RGB to lunimesence+chroma works. interesting and usefull

> Application error: a client-side exception has occurred (see the browser console for more information).

seems like website doesn't work without webgl enabled... why?

Application error: a client-side exception has occurred (see the browser console for more information).

Already posted here earlier: https://news.ycombinator.com/item?id=47376119

I usually have a script/alias cmd to automatically convert images to webp. The webp format has pretty much replaced jpg/jpeg (lacks transparency/alpha support) and png (no compression) formats for me.

There is also AVIF format which is newer and better but it needs to still mature a bit with better support/compatability.

If you are hosting images it is nice to use avif and fallback to webp.