Re: [PNG] Meeting topics - Nov 13th, 2023

RGBE is still pixel storage.  It is still about using RGB, though in a more HDR range.  According to https://en.wikipedia.org/wiki/RGBE_image_format  Also, according to that page, there is no formal standard for RGBE, only a reference to a proprietary document (without any licensing information) about an implementation in Radiance.  As such, I wouldn’t be in favor of supporting it in PNG.

I haven’t heard any specific use cases and/or users needing YUV, but would welcome to hear from some.

As for other things that aren’t necessary images – like motion vectors – it would be worthwhile hearing from specific users who believe that PNG (vs. various other existing options) is the right place to store such info.

Leonard

From: Chris Blume (ProgramMax) <programmax@gmail.com>
Date: Friday, November 10, 2023 at 1:37 PM
To: Leonard Rosenthol <lrosenth@adobe.com>
Cc: Richard Geldreich <rich@binomial.info>, public-png@w3.org <public-png@w3.org>
Subject: Re: [PNG] Meeting topics - Nov 13th, 2023

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You are right.
Rich had mentioned RGBE (rather than RGBA), where the E is a shared exponent. This is how the color model / data storage becomes a bit blurred.

There are other *true* color models like YUV that are worth considering. And there are also other blurring-the-lines ideas like storing normal maps, motion vectors, etc (not really color).

On Thu, Nov 9, 2023 at 10:47 PM Leonard Rosenthol <lrosenth@adobe.com<mailto:lrosenth@adobe.com>> wrote:
Changing the serialization of the pixel data (e.g. half-floats, or even full floats, from integers) is not the same thing as changing color models.

What other color models are we thinking about, Chris?

Leonard

From: Chris Blume (ProgramMax) <programmax@gmail.com<mailto:programmax@gmail.com>>
Date: Friday, November 10, 2023 at 12:48 AM
To: Richard Geldreich <rich@binomial.info<mailto:rich@binomial.info>>
Cc: public-png@w3.org<mailto:public-png@w3.org> <public-png@w3.org<mailto:public-png@w3.org>>
Subject: Re: [PNG] Meeting topics - Nov 13th, 2023

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Of course!
That is part of what I meant for the color models section. You had mentioned wanting to discuss it earlier so I wanted to include it.

On Thu, Nov 9, 2023 at 2:15 PM Richard Geldreich <rich@binomial.info<mailto:rich@binomial.info>> wrote:
Hi Chris - Could we also talk about half float PNG's? I've got some new developments that are very interesting.


On Thu, Nov 9, 2023 at 1:37 PM Chris Blume (ProgramMax) <programmax@gmail.com<mailto:programmax@gmail.com>> wrote:
Hello everyone,

Our next meeting is this coming Monday at 11am Eastern.

Topics:

  *   We're going to try a new Zoom link. I'll include both the new link and the old link in the calendar. If the new link doesn't work, try the old link.
  *   How could/should we add additional color models?

     *   PNG currently has a list of color models. If we want to add more color models, we could add to this list. That was the forward-compatibility intended by the list. It is also what we do with cICP.
     *   But adding to the list would break existing codecs. The key difference between this list and cICP here is without understanding an update to the CICP list (or even the cICP chunk itself), a decoder can still show an approximate representation. But a new item in the color model list does not have an equivalent approximation.
     *   We could have a new chunk signal the new color model. And there can be a fall-back approximate representation provided by the original list. This is effectively what happens now for normal maps, half-floats, etc.

  *   Marketing subgroup

     *   Stephanie is spearheading PNG Third Edition marketing. We're thinking of creating a subgroup to discuss how we plan to spread the word. Everyone in the main WG is welcome to join this subgroup. The intention of a subgroup is to not spam the main group.

Did I miss anything? Are there any other topics you all would like to discuss?

See you Monday!