JPEG XL reference implementation
This repository contains a reference implementation of JPEG XL (encoder and
libjxl. This software library is
used by many applications that support JPEG XL.
JPEG XL is in the final stages of standardization and its codestream and file format
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 format
specification and can be decoded with current and future
djxl decoders or
libjxl decoding library.
Quick start guide
For more details and other workflows see the “Advanced guide” below.
Checking out the code
git clone https://github.com/libjxl/libjxl.git --recursive --shallow-submodules
This repository uses git submodules to handle some third party dependencies
third_party, that’s why is important to pass
--recursive. If you
didn’t check out with
--recursive, or any submodule has changed, run:
git submodule update --init --recursive --depth 1 --recommend-shallow
--depth 1 --recommend-shallow options create
shallow clones which only downloads the commits requested, and is all that is
needed to build
libjxl. Should full clones be necessary, you could always run:
git submodule foreach git fetch --unshallow git submodule update --init --recursive
which pulls the rest of the commits in the submodules.
Important: If you downloaded a zip file or tarball from the web interface you
won’t get the needed submodules and the code will not compile. You can download
these external dependencies from source running
./deps.sh. The git workflow
described above is recommended instead.
Required dependencies for compiling the code, in a Debian/Ubuntu based
sudo apt install cmake pkg-config libbrotli-dev libgflags-dev
Optional dependencies for supporting other formats in the
in a Debian/Ubuntu based distribution run:
sudo apt install libgif-dev libjpeg-dev libopenexr-dev libpng-dev libwebp-dev
We recommend using a recent Clang compiler (version 7 or newer), for that
install clang and set
sudo apt install clang export CC=clang CXX=clang++
cd libjxl mkdir build cd build cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_TESTING=OFF .. cmake --build . -- -j$(nproc)
The encoder/decoder tools will be available in the
sudo cmake --install .
To encode a source image to JPEG XL with default settings:
build/tools/cjxl input.png output.jxl
For more settings run
build/tools/cjxl --help or for a full list of options
build/tools/cjxl -v -v --help.
To decode a JPEG XL file run:
build/tools/djxl input.jxl output.png
djxl are able to read/write the following
image formats: .exr, .gif, .jpeg/.jpg, .pfm, .pgm/.ppm, .pgx, .png.
For speed benchmarks on single images in single or multi-threaded decoding
djxl can print decoding speed information. See
djxl --help for details
on the decoding options and note that the output image is optional for
For more comprehensive benchmarking options, see the
Building with Docker
We build a common environment based on Debian/Ubuntu using Docker. Other
systems may have different combinations of versions and dependencies that
have not been tested and may not work. For those cases we recommend using the
Docker container as explained in the
step by step guide.
Building JPEG XL for developers
For experienced developers, we provide build instructions for several other environments:
- Building on Debian
- Building on Windows with vcpkg (Visual Studio 2019)
- Building on Windows with MSYS2
- Cross Compiling for Windows with Crossroad
If you encounter any difficulties, please use Docker instead.
Please note that the PATENTS file only mentions Google since Google is the legal
entity receiving the Contributor License Agreements (CLA) from all contributors
to the JPEG XL Project, including the initial main contributors to the JPEG XL
format: Cloudinary and Google.
- JPEG XL Format Overview
- Introductory paper (open-access)
- XL Overview – a brief introduction to the source code modules
- JPEG XL white paper
- JPEG XL official website
- JPEG XL community website
- More information on testing/build options
- Git guide for JPEG XL – for developers
- Fuzzing – for developers
- Building Web Assembly artifacts
- Test coverage on Codecov.io – for
- libjxl documentation on readthedocs.io
If you encounter a bug or other issue with the software, please open an Issue here.