Add PlatformImage.FromStreamAsync

[MartyIX]

Description of Change

It appears that on Windows, it's quite slow load many images using PlatformImage.FromStream because it uses an AsyncPump implementation.

I tested with the same batch of images and the load times differ significantly for me:

• main - 9 seconds
• PR - 1.3 seconds

TODO: Measure in Release configuration.

Issues Fixed

Fixes #

[dotnet-policy-service]

Hey there @MartyIX! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[MartyIX]

This won't be added because the benefit is too small for new API.

[MartyIX]

A workaround is:

using System.Threading;
using Microsoft.Graphics.Canvas;

// ...

#if WINDOWS
    [ThreadStatic]
    private static ICanvasResourceCreator? Creator;

    private static async Task<IImage> PlatformImageFromStreamAsync(Stream stream, ImageFormat format = ImageFormat.Png)
    {
        Creator ??= CanvasDevice.GetSharedDevice();

        if (Creator is null)
            throw new Exception("No resource creator has been registered globally or for this thread.");

        CanvasBitmap bitmap = await CanvasBitmap.LoadAsync(Creator, stream.AsRandomAccessStream());
        return new PlatformImage(Creator, bitmap);
    }
#else
    private static Task<IImage> PlatformImageFromStreamAsync(Stream stream, ImageFormat format = ImageFormat.Png)
        => Task.FromResult(PlatformImage.FromStream(stream, format));
#endif

[bronteq]

Try to propose anyway, maybe can be merged for .Net9

[MartyIX]

I have already discussed it with .NET MAUI developers. They don't find sufficient justification for adding new API at the moment.