[Cin] static hdr metadata generation ....

Found this code on github via some comment discussion https://github.com/HDRWCG/HDRStaticMetadata ah, such a mix of opencv/qtgui! but may be it exposes enough to make it into pure c++ pass? Still no idea how dynamic metadata work .. there are standarts but they a bit hard to read for me: https://pub.smpte.org/pub/st2094-10/st2094-10-2021.pdf https://pub.smpte.org/pub/st2094-40/st2094-40-2020.pdf Tonemapping using those already supported by ffmpeg's libplacebo filter, but this one need Vulkan driver/device! And how to *construct* those types of metadata is not clear for me .....