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This repository contains a reference implementation of JPEG XL (encoder and decoder), called libjxl. This software library is used by many applications that support JPEG XL.
JPEG XL was standardized in 2022 as ISO/IEC 18181. The core codestream is specified in 18181-1, the file format in 18181-2. Decoder conformance is defined in 18181-3, and 18181-4 is the reference software.
The library API, command line options, and tools in this repository are subject to change, however files encoded with cjxl conform to the JPEG XL specification and can be decoded with current and future djxl decoders or the libjxl decoding library.
In most Linux distributions, installing libjxl is just a matter of using the package management system. For example in Debian-based distributions: apt install libjxl-tools will install cjxl and djxl and other tools like benchmark_xl are available in the package libjxl-devtools. On MacOS, you can use Homebrew: brew install jpeg-xl.
The desired visual fidelity can be selected using the --distance parameter (in units of just-noticeable difference, where 0 is lossless and the most useful lossy range is 0.5 .. 3.0), or using --quality (on a scale from 0 to 100, roughly matching libjpeg). The encode effort can be selected using the --effort parameter.
