libjxl VS exiv2

> Regarding JPEG XL's mobile support, it makes sense it would see limited development if the company that manages one of the biggest mobile players has been the greatest restriction on their success. The lack of support also disincentivises manufacturers to prioritise support.

There was literally no involvement from any hardware vendor in the standardization of JPEG XL. It went from a Call for Proposals in Sept 2018 to Committee Draft in Aug 2019 with very little time for industry feedback. Contrast this with AV1 which had involvement from hardware vendors Intel, NVIDIA, Arm, AMD, Broadcom, Amlogic from the beginning as well as companies who ship media on hardware at scale such as Cisco, Netflix, Samsung and yes Google. These companies reviewed and provided significant feedback on the format that made it suitable for hardware implementation.

https://news.ycombinator.com/threads?id=JyrkiAlakuijala is a lead on the project and a Google employee, and active in JPEG XL development https://github.com/libjxl/libjxl/commits?author=jyrkialakuij...

https://github.com/libjxl/libjxl/blob/main/doc/format_overvi... is a pretty detailed but good overview. The highlights are variable size DCT (up to 128x128), ANS entropy prediction, and chroma from luminance prediction. https://github.com/libjxl/libjxl/blob/main/doc/encode_effort... also gives a good breakdown of features by effort level.

For JPEG XL, refer to its format overview [1]. In short its lossless mode uses a combination of multiple techniques: the rANS coding with an alias table, LZ77, reversible color transforms, a general vector quantization that subsumes palettes, a modified Haar transform and a learnable meta-adaptive decision tree for context modelling.

One good thing about JPEG XL is that its lossy mode also largely uses the same tool, with a major addition of specialized quantization and context modelling for low- and high-frequenty components.

[1] https://github.com/libjxl/libjxl/blob/main/doc/format_overvi...

The cjxl source is here. If you spot any reason why -x strip=exif may not work, tell me.

The problem is that the instructions for actually running the WASM file are not that clear... the docs the author mentions shows how to compile to WASM, which is easy enough, but then here's the instructions to make that actually work in the browser:

https://github.com/libjxl/libjxl/blob/main/tools/wasm_demo/R...

Yeah, you need some mysterious Python script, a JS service worker at runtime, choose whether you want the WASM or WASM_SIMD target, use a browser that supports Threads and SIMD if you chose that, make sure to serve everything with the appropriate custom HTTP headers... just reading that, I can see that to get this stuff working on non-browser WASM targets would likely require expertise in WASM, which is the point of the OP. WASM's UX is just not there yet.

https://github.com/libjxl/libjxl#usage

> Specifically for JPEG files, the default cjxl behavior is to apply lossless recompression and the default djxl behavior is to reconstruct the original JPEG file (when the extension of the output file is .jpg).

I mean compiling a bleeding edge kicad, inkscape or jpeg-xl is easy. But will probably trash your system if you already have an older version installed.

But you look at your image viewer that could have the lossless indicator? (and there is an issue open to add this indicator to the jxl files)

https://github.com/libjxl/libjxl/issues/432

A change causing a crash has been identified in this version, depending on how applications using exiv2 pass data to it: https://github.com/Exiv2/exiv2/issues/2649.

Complete release notes

In addition, this commit isn't available in 0.27.6 yet, so newer JXLs which use Brotli to compress metadata (e.g. files encoded with libjxl 0.7.0) will also show no metadata unless you build exiv2 from the main branch with BMFF (and rebuild dependents of exiv2).

Thanks for the reply. I went a little bit deeper to get more out of images metadata using Exiv2/exiv2. It's getting everything from "exif" to "xmp" tags. And it's fairly maintained ! Only drawback, it's not written in GO. So I'm gonna call it using the cmdline ^^.

some of these appear to not actually have curated tasks. it lists exiv2 for example which links to an issues tag on github, but it's empty https://github.com/Exiv2/exiv2/issues?q=label%3A%22good+firs...

"WebP has been supported since 2016. You're right. I should add JXL. We only need to add a few lines of code to support JXL/bmff. JXL/codestream is still being negotiated by the standards committee and will add ICC support. Exiv2 doesn't provide ICC support for every image format." https://github.com/Exiv2/exiv2/issues/1466

exiv2 is a similar, but different program than exiftool.

Does jhead, exiftool, exiv2, etc., allow me to use a command or a series of commands to accomplish this goal?

Great! Reading through issue 1503 though, this support is for EXIF and XMP data in the "container" version of the format. Support for an ICC profile in the "codestream" format (both bare files and inside a container format file) is in issue 1506 and left for future work. So the support is not complete, but a good step forward for the format.