ISO/IEC 18181-4:2022

Information technology - JPEG XL image coding system - Part 4: Reference software

This document provides reference implementations of ISO/IEC 18181-1 and ISO/IEC 18181-2. The software supports lossless and lossy compression of images and image sequences for a wide range of use cases such as (but not limited to) images with wide colour gamut and/or high dynamic range and responsive web images. This document includes source code and instructions for compilation and usage.

Technologies de l'information — Systѐme de codage d'images JPEG XL — Partie 4: Logiciel de référence

General Information

• Status: Published
• Publication Date: 04-Aug-2022
• ICS: 35.040.30 - Coding of graphical and photographical information
• Technical Committee: ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
• Drafting Committee: ISO/IEC JTC 1/SC 29/WG 1 - JPEG Coding of digital representations of images
• Current Stage: 6060 - International Standard published
• Start Date: 05-Aug-2022
• Due Date: 22-Jan-2022
• Completion Date: 05-Aug-2022

Relations

• Splited From: ISO/IEC 18181-1:2022 - Information technology - JPEG XL image coding system - Part 1: Core coding system
• Effective Date: 23-Apr-2020
• Consolidated By: ISO 17971:2025 - Textiles - Smart textiles - Test method for determining the screen-touch properties of fabrics
• Effective Date: 21-Sep-2024

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.

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 18181-4
First edition
2022-08
Information technology — JPEG XL
image coding system —
Part 4:
Reference software
Technologies de l'information — Systѐme de codage d'images JPEG
XL —
Partie 4: Logiciel de référence
Reference number
© ISO/IEC 2022
© ISO/IEC 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
© ISO/IEC 2022 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Reference software . 1
4.1 General . 1
4.2 Examples of use . 2
4.3 Access. 2
4.4 Dependencies . 3
5 Usage instructions . 3
iii
© ISO/IEC 2022 – All rights reserved

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work.
The procedures used to develop this document and those intended for its further maintenance
are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria
needed for the different types of document should be noted. This document was drafted in
accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives or
www.iec.ch/members_experts/refdocs).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC
list of patent declarations received (see https://patents.iec.ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see
www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
A list of all parts in the ISO/IEC 18181 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards
body. A complete listing of these bodies can be found at www.iso.org/members.html and
www.iec.ch/national-committees.
iv
© ISO/IEC 2022 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 18181-4:2022(E)
Information technology — JPEG XL image coding system —
Part 4:
Reference software
1 Scope
This document provides reference implementations of ISO/IEC 18181-1 and ISO/IEC 18181-2. The
software supports lossless and lossy compression of images and image sequences for a wide range
of use cases such as (
...