Re: ISO 22028-5 Support (adding dWLm (Diffuse White Luminance Metadata)

Yes, I (and hopefully Chris L. as well) am meeting with that group and ICC in Tokyo in February to coordinate future work on HDR and still images. Given that we have a number of issues on the table for that meeting – which can/will impact PNG – I would recommend that we don’t rush anything.

Leonard

From: Seeger, Chris (NBCUniversal) <Chris.Seeger@nbcuni.com>
Date: Sunday, December 10, 2023 at 9:31 AM
To: Chris Blume (ProgramMax) <programmax@gmail.com>, Leo Barnes <lbarnes@apple.com>
Cc: public-png@w3.org <public-png@w3.org>
Subject: ISO 22028-5 Support (adding dWLm (Diffuse White Luminance Metadata)

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Hi All,

Is it too late to add one more chunk to 3rd Edition that is inline with our MDCV efforts?

I was recently made aware of ISO 22028-5 which defines High dynamic range and wide colour gamut encoding for still images (HDR/WCG). It adds an additional metadata: Diffuse White Luminance Metadata. It’s a great companion to the new chunks we’ve added in PNG.  The ISO effort has defined one more important element that I’ve been proposing for SMPTE ST 2086 (and am close to bringing to SMPTE).

Diffuse White Luminance Metadata allows for improved tone-mapping because it establishes a point above which compression of highlights might begin.

It’s a simple two-byte additional chunk which I’ve authored to a branch if anyone wants to take a look (Issue #390).  I need a chunk value to insert to finish up.

Best,
Chris