https://bugs.kde.org/show_bug.cgi?id=492458
Bug ID: 492458
Summary: Supporting HDR gain map & Ultra HDR image
Classification: Applications
Product: krita
Version: 5.2.3
Platform: unspecified
OS: Unspecified
Status: REPORTED
Severity: wishlist
Priority: NOR
Component: File formats
Assignee: krita-bugs-n...@kde.org
Reporter: al...@alvinhc.com
Target Milestone: ---
There seems to be a new HDR image format gaining some traction. I haven't got a
good understanding of them yet, so I am just writing down some very rough
notes:
Gain Map spec draft by Adobe:
https://helpx.adobe.com/nz/camera-raw/using/gain-map.html
This seems to be in the process of being standardized as ISO/CD 21496-1.
A website with some info on gain map:
https://gregbenzphotography.com/hdr-photos/jpg-hdr-gain-maps-in-adobe-camera-raw/
## File format support:
Google's "Ultra HDR Image" format:
https://developer.android.com/media/platform/hdr-image-format
This seems to be a format Google has developed to encode gain map data into
JPEG in a backward-compatible way.
They also have a library for handling this:
https://github.com/google/libultrahdr
(This seems to be slightly different from Adobe's JPEG gain map, but I haven't
found the spec on that.)
Apple seems to use gain map in their HEIF photos (needs checking).
libavif and libjxl has experimental gain map reading and writing support API.
## Support in other software (as far as I know):
- Adobe Camera Raw seems to be able to output JPEG gain map images.
- Chrome is able to read and render such JPEG images (tested on Windows)
- Ultra HDR is supported on Android 14
- Google Pixel Camera can save Ultra HDR (tested on Pixel 6)
## Relevance to Krita:
- Krita may want to be able to import these files as HDR format.
- This format may be a good candidate for exporting HDR painting.
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