Set alpha and pixel format for Direct2D WIC bitmap

[hez2010]

What does the pull request do?

Set PixelFormat and AlphaFormat in Direct2D BitmapImpl.

What is the current behavior?

The rendering failed due to PixelFormat and AlphaFormat are null, and throws with a not supported exception.

What is the updated/expected behavior with this PR?

No exception thrown due to not supported.

[hez2010]

BTW I would like to switch to Vortice.Direct2D (https://github.com/amerkoleci/Vortice.Windows) in the future, as it is being actively maintained. But this package only supports .NET 7+, what do you think dropping the netstandard2.0 and net6.0 target from Avalonia.Direct2D?

[cla-avalonia]

• All contributors have signed the CLA.

[hez2010]

@cla-avalonia agree

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0048084-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[maxkatz6]

@hez2010 there were couple of attempts to use any other d2d integration: https://github.com/AvaloniaUI/Avalonia/pulls?q=is%3Apr+Vortice+is%3Aclosed
In general, there is very low interest from the core team to maintain any other rendering backend. And we keep sharpdx only to make sure that avalonia doesn't depend on skia way too much.

Saying this, it should be absolutely possible to implement an alternative rendering backend outside of the repo. With enabling private APIs access.

[hez2010]

And we keep sharpdx only to make sure that avalonia doesn't depend on skia way too much.

Yeah. I'm investigating D2D support as this can get rid of the dependency on Skia and Egl on Windows to save ~20 MB of binary size.

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0048086-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]