|Internet media type|
|Type of format||Lossy/lossless bitmap image format|
|Open format?||Yes (royalty-free)|
JPEG XL is a royalty-free 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.
The main features are:
JPEG XL is based on ideas from Google's PIK format and Cloudinary's FUIF format (which was in turn based on FLIF).
The format is mainly based on two encoding modes:
Both modes can be assisted by separate modeling of specific image features, unknown in other codecs at the time of creating the format:[a]
Lossy modes typically use the XYB color space derived from LMS.
JPEG XL can losslessly reencode existing JPEG files by directly copying JPEG's DCT block coefficients to 8x8 VarDCT blocks, making smaller filesizes possible due to better entropy coding. JPEG reconstruction data allows transcoding back to the original JPEG file, although constraints limit support for some files.
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 signaled tree structure and predictor selection per context. Entropy coding is LZ77-enabled and can use both asymmetric numeral systems (ANS) 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.
Animated (multi-frame) images do not perform advanced inter-frame prediction, though some rudimentary inter-frame coding tools are available:
|Initial release||December 27, 2019|
0.6.1 / October 30, 2021
|License||New BSD License (previously Apache License 2.0)|
In 2017, JTC1/SC29/WG1 (JPEG) issued a call for proposals for JPEG XL – the next generation image coding standard.
The file format (bitstream) was frozen on 25 December 2020 and formally standardized on 13 October 2021. Any file compliant to this standard is guaranteed to be decodable by all future releases.
|Common Name||Part||First public release date (First edition)||ISO/IEC Number||Formal Title|
|JPEG XL||Part 1||30 March 2022||ISO/IEC 18181-1||JPEG XL Image Coding System — Part 1: Core coding system|
|Part 2||13 October 2021||ISO/IEC 18181-2||JPEG XL Image Coding System — Part 2: File format|
|Part 3||under development, planned for 2022||ISO/IEC DIS 18181-3||JPEG XL Image Coding System — Part 3: Conformance testing|
|Part 4||under development, planned for 2022||ISO/IEC FDIS 18181-4||JPEG XL Image Coding System — Part 4: Reference software|
The current contributors have committed to releasing it publicly under a royalty-free and open source license.