# jpeg-xl **Repository Path**: mirrors_chromium_googlesource/jpeg-xl ## Basic Information - **Project Name**: jpeg-xl - **Description**: No description available - **Primary Language**: Unknown - **License**: BSD-3-Clause - **Default Branch**: upstream/master - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 0 - **Created**: 2021-03-19 - **Last Updated**: 2025-08-23 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README # JPEG XL reference implementation JXL logo This repository contains a reference implementation of JPEG XL (encoder and decoder), called `libjxl`. JPEG XL is in the final stages of standardization and its codestream format is frozen. The libraries 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 ```bash git clone https://gitlab.com/wg1/jpeg-xl.git --recursive ``` 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`. 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: ```bash 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: ```bash 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. For example, with clang-7: ```bash sudo apt install clang-7 export CC=clang-7 CXX=clang++-7 ``` ### Building ```bash cd jpeg-xl 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 ```bash sudo cmake --install . ``` ### Basic encoder/decoder To encode a source image to JPEG XL with default settings: ```bash 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: ```bash 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 a more comprehensive comparison of compression density between multiple options see "Benchmarking with benchmark_xl" section below. ## 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 environment as explained in the [step by step guide](doc/developing_in_docker.md). ### Building JPEG XL for developers For experienced developers, we also provide build instructions for an [up to date Debian-based Linux](doc/developing_in_debian.md) and [64-bit Windows](doc/developing_in_windows.md). If you encounter any difficulties, please use Docker instead. ## Benchmarking with benchmark_xl We recommend `build/tools/benchmark_xl` as a convenient method for reading images or image sequences, encoding them using various codecs (jpeg jxl png webp), decoding the result, and computing objective quality metrics. An example invocation is: ```bash build/tools/benchmark_xl --input "/path/*.png" --codec jxl:wombat:d1,jxl:cheetah:d2 ``` Multiple comma-separated codecs are allowed. The characters after : are parameters for the codec, separated by colons, in this case specifying maximum target psychovisual distances of 1 and 2 (higher implies lower quality) and the encoder effort (see below). Other common parameters are `r0.5` (target bitrate 0.5 bits per pixel) and `q92` (quality 92, on a scale of 0-100, where higher is better). The `jxl` codec supports the following additional parameters: Speed: `falcon`, `cheetah`, `hare`, `wombat`, `squirrel`, `kitten`, `tortoise` control the encoder effort in ascending order. This also affects memory usage: using lower effort will typically reduce memory consumption during encoding. * `falcon` disables all of the following tools. * `cheetah` enables coefficient reordering, context clustering, and heuristics for selecting DCT sizes and quantization steps. * `hare` enables Gaborish filtering, chroma from luma, and an initial estimate of quantization steps. * `wombat` enables error diffusion quantization and full DCT size selection heuristics. * `squirrel` (default) enables dots, patches, and spline detection, and full context clustering. * `kitten` optimizes the adaptive quantization for a psychovisual metric. * `tortoise` enables a more thorough adaptive quantization search. Mode: JPEG XL has two modes. The default is Var-DCT mode, which is suitable for lossy compression. The other mode is Modular mode, which is suitable for lossless compression. Modular mode can also do lossy compression (e.g. `jxl:m:q50`). * `m` activates modular mode. Other arguments to benchmark_xl include: * `--save_compressed`: save codestreams to `output_dir`. * `--save_decompressed`: save decompressed outputs to `output_dir`. * `--output_extension`: selects the format used to output decoded images. * `--num_threads`: number of codec instances that will independently encode/decode images, or 0. * `--inner_threads`: how many threads each instance should use for parallel encoding/decoding, or 0. * `--encode_reps`/`--decode_reps`: how many times to repeat encoding/decoding each image, for more consistent measurements (we recommend 10). The benchmark output begins with a header: ``` Compr Input Compr Compr Compr Decomp Butteraugli Method Pixels Size BPP # MP/s MP/s Distance Error p norm BPP*pnorm Errors ``` `ComprMethod` lists each each comma-separated codec. `InputPixels` is the number of pixels in the input image. `ComprSize` is the codestream size in bytes and `ComprBPP` the bitrate. `Compr MP/s` and `Decomp MP/s` are the compress/decompress throughput, in units of Megapixels/second. `Butteraugli Distance` indicates the maximum psychovisual error in the decoded image (larger is worse). `Error p norm` is a similar summary of the psychovisual error, but closer to an average, giving less weight to small low-quality regions. `BPP*pnorm` is the product of `ComprBPP` and `Error p norm`, which is a figure of merit for the codec (lower is better). `Errors` is nonzero if errors occurred while loading or encoding/decoding the image. ## License This software is available under a 3-clause BSD license which can be found in the [LICENSE](LICENSE) file, with an "Additional IP Rights Grant" as outlined in the [PATENTS](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 * [Introductory paper](https://www.spiedigitallibrary.org/proceedings/Download?fullDOI=10.1117%2F12.2529237) (open-access) * [XL Overview](doc/xl_overview.md) - a brief introduction to the source code modules * [JPEG XL white paper](http://ds.jpeg.org/whitepapers/jpeg-xl-whitepaper.pdf) * [JPEG XL website](https://jpeg.org/jpegxl/) * [Jon's JXL info page](https://sneyers.info/jxl/) ### Development process * [Docker setup - **start here**](doc/developing_in_docker.md) * [Building on Debian](doc/developing_in_debian.md) - for experts only * [Building on Windows](doc/developing_in_windows.md) - for experts only * [More information on testing/build options](doc/building_and_testing.md) * [Git guide for JPEG XL](doc/developing_in_github.md) - for developers only * [Building Web Assembly artifacts](doc/building_wasm.md) ### Contact If you encounter a bug or other issue with the software, please open an Issue here. There is a [subreddit about JPEG XL](https://www.reddit.com/r/jpegxl/), and informal chatting with developers and early adopters of `libjxl` can be done on the [JPEG XL Discord server](https://discord.gg/DqkQgDRTFu).