ISO/IEC 15444-2:2023

Overview

ISO/IEC 15444-2:2023 - "Information technology - JPEG 2000 image coding system - Part 2: Extensions" defines the extended features of the JPEG 2000 ecosystem. This third-edition standard specifies both lossless (bit‑preserving) and lossy compression methods for continuous‑tone, bi‑level, grey‑scale, colour and multi‑component still images. It standardizes extended decoding processes, an extended codestream syntax, an extended file format (JPX), a metadata container and a set of image metadata, plus guidance for extended encoding and practical implementation.

Key topics and technical requirements

• Extended codestream syntax and marker segments to support richer signalling and interoperability.
• JPX extended file format: fragmentation of codestreams, multi‑codestream files, reader requirement masks and defined box structures for metadata.
• Metadata container and standard metadata set enabling robust image description, interchange and conformance checks.
• Wavelet and transform extensions: arbitrary and whole‑sample symmetric wavelet transforms, single‑sample overlap, and general decomposition support for flexible transform designs.
• Quantization and coding improvements: variable scalar quantization, trellis coded quantization (TCQ), and block coder extensions for improved rate‑distortion tradeoffs.
• Visual masking and non‑linear transforms to exploit human visual perception for better compression efficiency.
• Region of Interest (ROI) coding and extraction mechanisms to prioritize important image regions during compression and decoding.
• Multiple component transformations for multi‑channel imagery and multi‑component collections.
• Compatibility and examples: guidelines, examples (including wrapping other codestreams), and conformance rules. Note: the standard was prepared in collaboration with ITU‑T (Rec. ITU‑T T.801) and may involve patented technologies-implementers should consult ISO/IEC patent resources.

Practical applications

• High‑quality archival storage and digital preservation (museums, libraries, archives) using lossless JPEG 2000 and metadata-rich JPX files.
• Remote sensing, medical imaging and scientific imaging where multi‑component images and ROI coding are critical.
• Broadcast, film and photography workflows requiring progressive decoding, high dynamic range support and advanced wavelet transforms.
• Software libraries, codec developers and imaging tool vendors implementing JPEG 2000 features for interoperable file exchange.

Who should use this standard

• Codec and imaging software developers, systems integrators, digital archivists, standards bodies and organizations requiring stable, interoperable image compression and metadata handling.

Related standards

• ISO/IEC 15444 series (Part 1 - baseline JPEG 2000 codestream specification) and ITU‑T Rec. T.801 (equivalent text preparation). Before implementation, check patent notices at ISO’s patent database.