JPEG XL is a raster-graphics file format that supports both lossy and lossless compression. It is designed to outperform existing raster formats and thus to become their universal replacement.[2]

Name

JPEG means Joint Photographic Experts Group.
X is part of JPEG standards since 2000.
L means Long-term because the authors' intention for the format is to replace the legacy JPEG and last as long too.[3]

History

In 2017, JTC1/SC29/WG1 issued a Call for proposals for JPEG XL – the next generation image coding standard.[4]

The file format (bitstream) was frozen on December 25, 2020, meaning that the format is now guaranteed to be decodable by future releases.[5]

Features

The main features are:[6]

  • Faster compression than H.265 HEVC HM, Daala and WebP and fast decoding;
  • Support for a variety of color spaces, providing wide color gamut, higher bit depths and high dynamic ranges;
  • High-quality compression of synthetic images, such as bitmap fonts and gradients;
  • Inherently responsive / progressive encoding;
  • Lossless encoding and lossless alpha encoding;
  • Image region coding;
  • Low-complexity encoding;
  • Animation;
  • Lossless transcoding of legacy JPEG images with ~20% size reduction;[7]
  • Royalty-free format with an open-source reference implementation.[8]

Technical details

JPEG XL is based on ideas from Google's Pik format and Cloudinary's FUIF format.

The format has a variety of encoding modes. On the legacy side, it has a mode that transcodes legacy JPEG in a more compact way for storage. On the more modern side, it has a VarDCT-based lossy mode (with separate modeling of shapes and repeating "patches" like text) and a near-lossless/responsive mode using a Haar-like transform. The DCT uses a XYB color space derived from LMS.[9]

Prediction is run using a pixel-by-pixel decorrelator without side information, including a parametrized self-correcting weighted ensemble of predictors. Context modeling includes specialized static models and powerful meta-adaptive models that take local error into account, with a signalled tree structure and predictor selection per context. Entropy coding is LZ77-enabled and can use both Asymmetric Numeral Systems and Huffman coding (for low complexity encoders or for reducing overhead of short streams).

It defaults to a visually near-lossless setting that still provides good compression.[10]

Animated (multi-frame) images do not perform inter-frame prediction – unlike the video codec-based formats.[10]

Software

Existing support

Proposed support

Standardization status

Common Name Part First public release date (First edition) ISO/IEC Number ITU Number Formal Title
JPEG XL Part 1 under development ISO/IEC FDIS 18181-1 JPEG XL Image Coding System — Part 1: Core coding system
Part 2 under development ISO/IEC FDIS 18181-2 JPEG XL Image Coding System — Part 2: File format
Part 3 under development ISO/IEC WD 18181-3 JPEG XL Image Coding System — Part 3: Conformance testing
Part 4 under development ISO/IEC CD 18181-4 JPEG XL Image Coding System — Part 4: Reference software

References

  1. ^ a b "fuif/README.md". GitHub. Retrieved 2019-04-04.
  2. ^ https://tech.slashdot.org/story/19/08/17/1855214/can-jpeg-xl-become-the-next-free-and-open-image-format
  3. ^ a b https://gitlab.gnome.org/GNOME/gimp/-/issues/4681
  4. ^ "JPEG - Next-Generation Image Compression (JPEG XL) Final Draft Call for Proposals". Jpeg.org. April 23, 2018. Retrieved 29 May 2018.
  5. ^ "v0.2 JPEG XL Reference Software". GitLab.
  6. ^ "JPEG XL reaches Committee Draft". JPEG Org. 3 August 2019. Archived from the original (html) on 3 August 2019. Retrieved 3 August 2019. The current contributors have committed to releasing it publicly under a royalty-free and open source license.
  7. ^ https://jpeg.org/items/20190803_press.html
  8. ^ "jpeg / JPEG XL Reference Software". GitLab.
  9. ^ Alakuijala, Jyrki; van Asseldonk, Ruud; Boukortt, Sami; Szabadka, Zoltan; Bruse, Martin; Comsa, Iulia-Maria; Firsching, Moritz; Fischbacher, Thomas; Kliuchnikov, Evgenii; Gomez, Sebastian; Obryk, Robert; Potempa, Krzysztof; Rhatushnyak, Alexander; Sneyers, Jon; Szabadka, Zoltan; Vandervenne, Lode; Versari, Luca; Wassenberg, Jan (6 September 2019). Tescher, Andrew G; Ebrahimi, Touradj (eds.). "JPEG XL next-generation image compression architecture and coding tools". Applications of Digital Image Processing XLII: 20. doi:10.1117/12.2529237. ISBN 9781510629677.
  10. ^ a b Sneyers, Jon. "How JPEG XL Compares to Other Image Codecs". Cloudinary.
  11. ^ https://imagemagick.org/script/formats.php#supported
  12. ^ https://www.xnview.com/mantisbt/view.php?id=1845
  13. ^ https://bugzilla.mozilla.org/show_bug.cgi?id=1539075
  14. ^ https://bugs.chromium.org/p/chromium/issues/detail?id=1178058
  15. ^ https://bugs.webkit.org/show_bug.cgi?id=208235

External links