Overview
ISO/IEC 18181-4:2022 specifies the reference software implementation for the JPEG XL image coding system. This international standard provides source code and detailed instructions for compiling and using encoder and decoder software that conform to the core coding system (ISO/IEC 18181-1) and the file format specifications (ISO/IEC 18181-2). The reference software supports both lossless and lossy image compression, handling still images and image sequences efficiently.
JPEG XL is designed for modern image applications, including images with a wide color gamut, high dynamic range (HDR), and responsive web images, making it suitable for a broad range of multimedia and information technology use cases.
Key Topics
- Reference encoder and decoder software: Implements encoding and decoding compliant with ISO/IEC 18181-1 and ISO/IEC 18181-2.
- Lossless and lossy compression: Enables flexible compression options that preserve image quality or optimize file size.
- Wide color gamut and HDR support: Tailored for high-fidelity images with extended color and dynamic properties.
- Source code availability: Includes complete source code with build instructions in a README.md file.
- Compatibility and extensibility: Encoder and decoder can be integrated into image authoring and editing applications supporting JPEG XL.
- Supported image formats: Supports various input/output formats including PNG, EXR, GIF, JPEG, and formats such as PPM, PGX, PGM, and PFM.
- Dependencies: Utilizes libraries like highway, brotli, lcms2/skcms for ICC profile processing, and optionally IQA-optimization, VMAF for quality assessment.
- Access and compilation: Software provided electronically through ISO's official standards portal with clear usage and build instructions.
Applications
The reference software and JPEG XL coding system are highly applicable in:
- Web imaging and responsive design: Efficiently compress high-quality images for faster loading times without sacrificing visual quality.
- Digital photography and archiving: Safeguard image quality in lossless mode for professional photo storage and editing workflows.
- Multimedia content delivery: Optimize image sequences and static images used in video editing, streaming platforms, and interactive media.
- High dynamic range imaging: Support for HDR formats enables richer visual experiences in displays and digital cinema.
- Image editing software integration: Implementations can embed the reference encoder or decoder to support JPEG XL input/output.
- Conformance testing: Provides tools for verifying compliance of encoders and decoders with JPEG XL standards.
Related Standards
Understanding ISO/IEC 18181-4 benefits from familiarity with:
- ISO/IEC 18181-1:2021 – Core coding system of JPEG XL, defining syntax and compression mechanisms.
- ISO/IEC 18181-2:2021 – File format specification for JPEG XL, detailing container structure.
- ISO/IEC Directives, Part 1 and Part 2 – Guidelines on standard development and editorial procedures applicable to this standard.
- Other multimedia coding standards by ISO/IEC SC 29 – For broader context on image, audio, and video coding systems.
Practical Benefits
Utilizing the ISO/IEC 18181-4 reference software enables developers and organizations to:
- Quickly prototype JPEG XL-compliant encoding and decoding solutions.
- Evaluate the trade-offs between image quality and compression efficiency.
- Ensure compliance with international standards to guarantee interoperability.
- Support modern imaging requirements such as HDR and wide gamut for next-generation media.
- Streamline integration into existing workflows with open, well-documented software.
By adhering to ISO/IEC 18181-4, users gain access to a robust foundation for implementing and testing JPEG XL technology, supporting innovation and consistent image quality across platforms and devices.
Keywords: ISO/IEC 18181-4, JPEG XL, reference software, image coding, lossless compression, lossy compression, high dynamic range, wide color gamut, responsive web images, image encoder, image decoder, multimedia standards.