Enabling/extending available PixelFormats

The set of available PixelFormats is rather limited compared to the formats available in [WIC](https://docs.microsoft.com/en-us/windows/win32/wic/-wic-codec-native-pixel-formats) (which is extensible as well).

On several occasions I was looking for Rgb128Float and in my most recent project I would have used Bgr48 and the generic 3-4 channels if they were available.

There does not seem to be a public API to specify pixel format by GUID either - is it only question of defining the members and letting WIC do the heavy work, or does WPF actually have to implement any pixel format specific conversions itself?