7.0 KiB
JPEG XL reference implementation
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 is in the final stages of standardization and its codestream and file format are frozen.
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
under 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
The --shallow-submodules and --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.
Installing dependencies
Required dependencies for compiling the code, in a Debian/Ubuntu based distribution run:
sudo apt install cmake pkg-config libbrotli-dev
Optional dependencies for supporting other formats in the cjxl/djxl tools,
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 CC and CXX variables.
sudo apt install clang
export CC=clang CXX=clang++
Building
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 build/tools directory.
Installing
sudo cmake --install .
Basic encoder/decoder
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
run build/tools/cjxl -v -v --help.
To decode a JPEG XL file run:
build/tools/djxl input.jxl output.png
When possible cjxl/djxl are able to read/write the following
image formats: .exr, .gif, .jpeg/.jpg, .pfm, .pgm/.ppm, .pgx, .png.
Benchmarking
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
benchmarking purposes.
For more comprehensive benchmarking options, see the benchmarking guide.
Advanced guide
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.
License
This software is available under a 3-clause BSD license which can be found in the LICENSE file, with an "Additional IP Rights Grant" as outlined in the PATENTS file.
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.
Additional documentation
Codec description
- 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
Development process
- 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 developers
- libjxl documentation on readthedocs.io
Contact
If you encounter a bug or other issue with the software, please open an Issue here.
There is a subreddit about JPEG XL, and
informal chatting with developers and early adopters of libjxl can be done on the
JPEG XL Discord server.