PNGfor

PNGfor is a proposed extension to the Portable Network Graphics (PNG) image format developed by the PNG Forum Working Group to address enhanced metadata support, color management, and extensibility while maintaining backward compatibility with standard PNG decoders. It aims to keep PNG’s lossless compression and broad compatibility while providing a path for richer data in a single file.

The design centers on introducing optional ancillary chunks and structures that can carry rich metadata (including XMP and ICC profiles), accessibility information, time-based frames for animation, and references to external resources. These chunks are designed to be ignored by decoders that do not recognize them, preserving full image rendering. The goal is to provide a single-file container that remains compact and lossless, ensuring that existing workflows remain functional even if the PNGfor features are not used.

Technical details: PNGfor defines a small set of new chunk types with four-letter codes and a governance model for ownership and extension. It builds on the existing PNG chunk architecture (IHDR, IDAT, IEND, and ancillary chunks) and remains interoperable with existing tools that do not parse the new chunks. The specification emphasizes explicit versioning and clear demarcation between baseline PNG and PNGfor features.

Adoption and usage: PNGfor is not yet a formal standard; it is under experimental development with early implementations in open-source libraries and imaging pipelines. In practice, PNGfor is used to embed workflow metadata in archival images, enable color management workflows, and experiment with optional animation or interactivity features.

See also: PNG, APNG, WebP, ICC profiles, XMP.