[cubefox]

Here are visual comparisons between AVIF and JPEG XL on some test images with various bitrates / quality levels:

https://afontenot.github.io/image-formats-comparison/#end-of...

It seems AVIF has better compression at lower bit rates. At high bit rates they seem similar. AVIF especially shines for pictures with large homogeneous surfaces like the sky.

However, AVIF is missing some important features, such as progressive image loading. The maximum resolution is apparently also quite limited.

[networked]

A recent comment (https://news.ycombinator.com/item?id=36286548) made me notice chroma contamination in low-BPP JPEG XL in this comparison. Since then, I have been leaning towards adopting AVIF for medium-low-quality pictures, especially of people. (People will be unhappy if their teeth are yellowed in post-production.) I am not so sure about AVIF and the sky. A reply to the comment I have linked shows an example where AVIF smooths out a complex sky texture at every tested quality setting, but JPEG XL does not: https://afontenot.github.io/image-formats-comparison/#reykja....

AVIF is missing JPEG XL's ability to re-encode JPEGs losslessly and reversibly with a reduction in file size. It may prove a serious advantage for JPEG XL. AVIF also lacks anything like https://jpegxl.info/art/. :-)

[cubefox]

I also noticed more chroma contamination in JPEG XL, and overall more "ringing" artifacts.

Yeah, AVIF seems to remove noise fairly aggressively, or what it assumes to be noise. I think it looks pretty good in this sky example, although not overly faithful. It's less good when the removed "noise" is actual high frequency detail, e.g. on the fur of animals.

But what I meant with AVIF being good at homogeneous surfaces is that it apparently uses them sometimes to "save" bit rate, and to use it instead in other portions of the picture. Images with large surface portions tend to look significantly better in the rest of the image, e.g.

https://afontenot.github.io/image-formats-comparison/#clovis...

https://afontenot.github.io/image-formats-comparison/#us-ope...

I think here AVIF "small" looks overall better than JPEG XL "medium", e.g. in the details of the middle balloon basket, or the face of the tennis player.

I still think the lack of any progressive image loading makes AVIF completely unsuited for the web. The picture will only show once it was downloaded completely. That's a big step back from JPEG, and even more so from JPEG XL.

[JyrkiAlakuijala]

The 'Large' is still relatively low quality -- you can observe this by 3x zooming and comparing to original.

You can easily see that AVIF blurs (beautifies faces) and removes properties of the red cloth in the 'end-of-show' image.

Internet average image quality is higher than the 'Large' setting, so those names are not representative of actual internet use. Camera and image processing use is even of much higher quality.

[cubefox]

No, I think Internet average quality is a lot lower than AVIF or JPEG XL at "large". Instead of using such a high bitrate to save a small amount quality, it makes much more sense to use a low bit rate with a significantly higher resolution, and end up with the same file size.

Even cameras often have relatively little detail per pixel, since they do interpolate a lot of information due to the usage of Bayer filters (which record only one primary color per pixel instead of full RGB values), and because anything with less than perfect lighting will be somewhat noisy and blurry anyway.

[JyrkiAlakuijala]

I made quite a bit of unpublished effort to understand the average quality. Web almanac media chapter is showing average jpeg bpp density. In my collection median quality as reported by image magic is 85 and roughly 2–2.5 BPP.

[account42]

Compare the AVIF with the original and you see how bad it is. You need to make the comparison at a bitrate where at least one of the format gives acceptable results.