science

JPEG XL

JPEG XL is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand JPEG XL rather than just read about it. In short: The JPEG XL Image Coding System (JPEG XL, sometimes shortened to JXL) is an image format that supports both lossy and lossless compression. It was developed by the Joint Photographic Experts Group (JPEG), Google and Cloudinary.

Key takeaways

JPEG XL belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect JPEG XL to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of JPEG XL from memory before moving on to harder problems.

Reference excerpt

The JPEG XL Image Coding System (JPEG XL, sometimes shortened to JXL) is an image format that supports both lossy and lossless compression. It was developed by the Joint Photographic Experts Group (JPEG), Google and Cloudinary. It is a free and open standard defined by ISO/IEC 18181. The standard consists of four parts that cover the Core coding system, File format, Conformance testing, and Reference software, respectively. JPEG XL features a lossy compression mode called VarDCT built on block-based transform coding, which is similar to — but significantly improves and expands upon — the compression method of JPEG, and a modular mode that allows different features of the format to be combined in a "modular" way. Modular mode can be used either for lossless image compression, similar to PNG, or as a means to achieve lossy compression in a different way from VarDCT. The name refers to the design committee (JPEG), the X designates the series of its image coding standards published since 2000 (JPEG XT/XR/XS), and L stands for "long-term", highlighting the intent to create a future-proof, long-lived format to succeed JPEG/JFIF.

Positioning JPEG XL was designed to become a universal replacement for all established raster formats for the Web. To reach widespread adoption (unlike previous attempts, including several JPEG standards), the designers hope for beneficial network effects by offering the single best option for as many popular use cases as possible. To that end, the format offers significant improvements over all other (established) options with a comprehensive set of useful properties, geared especially towards accessibility over the Web and a smooth upgrade path, in combination with uncompromisingly powerful, yet efficiently computable compression and efficient data representation. Following a study about the most popular JPEG quality on the Web, developers paid special attention to the range with negligible or no perceived loss, and the default settings were adjusted accordingly. Several serious attempts at replacing JPEG that provided poor support for the high end of the quality range have failed. The JPEG XL call for proposals talks about the requirement of substantially better compression efficiency (60% improvement) comparing to JPEG. The standard is expected to outperform the still image compression performance shown by HEIC, AVIF, WebP, and JPEG 2000.

History In 2015, Jon Sneyers of the company Cloudinary published his Free Lossless Image Format (FLIF) on which he based his standardization proposal, called the Free Universal Image Format (FUIF), that begot JXL's "modular mode". In 2017 Google's data compression research team in Zurich published the PIK format, the prototype for the frequency transform coding mode. In 2018, the Joint Photographic Experts Group (JTC1 / SC29 / WG1) published a call for proposals for JPEG XL, its next-generation image coding standard. The proposals were submitted by September 2018. From seven proposals, the committee selected two as the starting point for the development of the new format: FUIF and PIK. In July 2019 the committee published a draft, mainly based on a combination of the two proposals. The bitstream was informally frozen on 24 December 2020 with the release of version 0.2 of the libjxl reference software. The file format and core coding system were formally standardized on 13 October 2021 and 30 March 2022 respectively.

Industry support and adoption

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with JPEG XL

Start with the simplest possible case. Write down what JPEG XL claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to JPEG XL before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about JPEG XL ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of JPEG XL

In research: JPEG XL appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses JPEG XL in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: JPEG XL is common in secondary-school and first-year university syllabi. It links to neighbouring topics Animated graphics file formats, Graphics standards, ISO standards, so understanding it makes those chapters shorter.
In everyday life: Look for JPEG XL outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study JPEG XL in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what JPEG XL means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain JPEG XL out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is JPEG XL in simple terms?

Why does JPEG XL matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study JPEG XL?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on JPEG XL.