Re: [PNG] Meeting discussion topics

On Sat, Sep 28, 2024 at 5:09 PM Chris Lilley <chris@w3.org> wrote:

> I'm on travel back from W3C TPAC, so won't be able to make this meeting.
> On 2024-09-28 03:24, Chris Blume (ProgramMax) wrote:
>
> Hello everyone,
>
> We will be holding a meeting this coming Monday, Sep 30th, 2024.
> I apologize for not getting the mail out sooner.
> I've gathered some topics we need to discuss.
>
>    - Some of us were added as "authors", but I believe we should be in
>    the "editors" list. I have a PR out for this
>    <https://github.com/w3c/png/pull/466>.
>    - mDCv & cLLi are safe-to-copy
>    <https://www.w3.org/TR/png-3/#5Chunk-naming-conventions>. But perhaps
>    they shouldn't be. If a user opens an image in an old editor, modifies the
>    file by drawing on top (with color values that ignored mDCv & cLLi chunks
>    because it was an old editor), the saved file shouldn't keep mDCv & cLLi,
>    right?
>    - Brought up in libpng issue 509
>    <https://github.com/pnggroup/libpng/issues/509>, mDCv
>    <https://www.w3.org/TR/png-3/#mDCv-chunk> doesn't specify how the
>    bytes are encoded.
>
> What is undefined about
>
> > The color primaries are encoded as three pairs of PNG two-byte unsigned
> integers,
>
Absolutely nothing.  I don't think that was Chris's point.  However you
might care to explain how to encode a volume expressed in the ACES AP0
primaries.  Completely off topic of course.