Dear all,
Just to follow up on an action item in the minutes:
Android has documentation about its use of PNG gainmaps for the screenshot
use case:
https://source.android.com/docs/core/graphics/hdr-screenshots#android16-hdr-shot
While it provides a general gainmap framework that we might want to
consider for PNG 4e, the spec does not document how ISO metadata is encoded.
Android source code documents how Android encodes PNGs with gainmaps here:
https://cs.android.com/android/platform/superproject/main/+/main:external/skia/src/encode/SkPngEncoderImpl.cpp;l=299;drc=0d94e966268bbc200ea57e074f33afca6321e483
With the gaimap serialization happening here:
https://cs.android.com/android/platform/superproject/main/+/main:external/skia/src/codec/SkGainmapInfo.cpp;l=246;drc=61197364367c9e404c7da6900658f1b16c42d0da
Sincerely,
Fares
On Mon, Jul 7, 2025 at 8:31 AM Chris Blume (ProgramMax) <
programmax@gmail.com> wrote:
> Attached is a PDF of the meeting minutes from Jul 7th, 2025.
>
> Executive summary:
>
> - Gain maps & gain curves waiting on their respective specs to be made
> publicly available.
> - Google has an implementation of PNG gain maps which they use to take
> HDR screenshots. So there is certainly interest.
> - Spec update coming to add negative cHRM values.
>
> Our next meeting is Jul 21st, 2025.
> See you then!
>