Add PNG dWLm (Diffuse white luminance metadata ) chunk to conform to ISO 22028-5 #390
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ISO 22028-5 High dynamic range and wide colour gamut encoding for still images (HDR/WCG) identifies a very important parameter (Diffuse white luminance metadata ).
This metadata allows us to determine at which point highlight compression might occur during HDR to SDR conversion.
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palemieux commentedon Dec 10, 2023
What is the relationship between diffuse white luminance metadata and reference white specified in Report ITU-R BT.2408?
digitaltvguy commentedon Dec 11, 2023
Sounds like this will get added for 4th Edition.
ProgramMax commentedon Feb 28, 2025
It sounds like ISO 22028-5 will be paywalled when published.
Is ITU-R BT.2408 effectively the same (and not paywalled)?
svgeesus commentedon Apr 14, 2025
svgeesus commentedon Apr 14, 2025
In the new version of 22028-5, what was previously called Reference White is now renamed to HDR Reference White for clarity.
BT.2048 already defines, in section 2.1, HDR Reference White and does so the same as 22028-5.
svgeesus commentedon Apr 14, 2025
So in practice, the metadata is a way to override the definition in BT.2048, ie when the luminance is not 203
leo-barnes commentedon Apr 15, 2025
Yep, pretty much. IIRC 203 nits is just a default, but before there was not really any way to signal anything other than the default.