Re: [PNG] Meeting topics

Regrets for today's meeting.

Chris
________________________________
From: Chris Blume (ProgramMax) <programmax@gmail.com>
Sent: 26 September 2025 20:11
To: Portable Network Graphics (PNG) Working Group <public-png@w3.org>
Subject: [PNG] Meeting topics


External: Think before clicking

Hello everyone,
We have a meeting this coming Monday. Here are some topics we can discuss. Feel free to reply with any topics you would like to add/alter.

  *   Discussion topics
     *   C2PA<https://spec.c2pa.org/specifications/specifications/2.2/specs/C2PA_Specification.html#_embedding_manifests_into_png> (provenance and authenticity)
        *   Last time, we asked how widely used it is. It sounds like billions of PNGs have been produced with the 'caBX' chunk, since AI systems include it when producing images.
        *   Given this many images with 'caBX', perhaps we don't need to rename the chunk to 'cABX' when adding it to the spec.
     *   SMPTE ST 2094-10<https://github.com/w3c/png/issues/311> (tone mapping metadata)
        *   We're waiting for more information. As such, this might be more of a status update report here than a discussion topic.
     *   SMPTE 2094-50<https://github.com/SMPTE/st2094-50> (gain curves)
        *   A draft was just made public 3 days ago (follow link above).
        *   Should we add a chunk for this?
        *   T.35<https://www.itu.int/rec/T-REC-T.35-200002-I> is related.
     *   ISO 21496-1<https://www.iso.org/standard/86775.html> (gain maps)
        *   Any update on ISO possibly making this freely available?
        *   Last meeting, we learned that W3C strongly prefers referencing freely available specs but makes exceptions. And that ISO is unlikely to make specs free (although, I recall we managed this in the past?).
        *   If it seems unlikely for the spec to become freely available, should we continue with some new chunks?
  *   Updates
     *   Apple will help with the iDOT extension.
     *   FileReadSpeedTest<https://github.com/ProgramMax/FileReadSpeedTest> tool created to help identify & test decoding performance goals.