avif file gets decoded into another colorspace

[Particlo]

this https://us.zonerama.com/willskiadventures/Photo/1000114927/1005688382
which has bt2020 color space
gets decoded into a bitmap which has scRGB color space
why?

[awxkee]

As I noted here #35 (comment): decoding and encoding using DataSpace/ColorSpace is not implemented. Any image is tonemapped to sRGB.
I created the library before HDR displays became common ( and even there was no API to set DataSpace/ColorSpace outside of android internals ), and back then, tone mapping suited me well.
Now HDR screens are more common, and API is here, but I still don't need it.

DataSpace/ColorSpace is not really documented, IIRC they can't be set on F16 image ( probably on RGBA_1010102 also, but thats needs to be tested ), they don't supported by API level before 30, so linking and using from C++ those bitmap APIs is a tricky.
Writing enum to match CICP with DataSpace is more or less straightforward, but linking different methods for different OS API version, and testing undocumented capabilities of DataSpace/ColorSpace is not.
Thus, I think at least a dozen hours of labor required to do so if someone wants to implement it.

[Particlo]

could this be solved by creating another decoding function that instead of outputting a Bitmap it outputs the data directly from the decoder? could this also remove a copypaste from decoder output buffer to Bitmap buffer

[awxkee]

No, this is actually a really bad workaround. It will eliminate linking issues but introduce OOM and memory management problems on the JVM (or KVM) side, because it requires to manage large memory chunks in Kotlin/Java.
Linking issues are a headache that might take a few hours to resolve, but handling large buffers in Kotlin/Java is a long-term ( it's doomed ) problem that could lead to bugs that are difficult to track down for years.