Drawing a geometry onto a Bitmap (Avalonia)

Question

My question is pretty straight forward: Is it possible to draw a Avalonia.Media.Geometry onto a Avalonia.Media.Bitmap so that I can save the resulting Image to a Steam as well as use the whole thing with an ImageBrush?

In the System.Drawing namespace one could simply call Graphics.FromImage(mySystemDrawingBitmap); to get a Graphics object which can then be used to draw whatever geometry you want.

Is there a similar easy approach to this in Avalonia? I dug up something called RenderTargetBitmap from the documentation which looks promising as it has a method called CreateDrawingContext but it apparently needs an IVisualBrushRenderer (whatever that may be) instance as a parameter to work. There seems to be a thing called ImmediateRenderer that implements said interface however it requires an Avalonia.VisualTree.IVisual itself as a parameter in it's constructor and at this stage I'm kinda doubting the usefulness of the RenderTargetBitmap for my problem as it seems to have a massive overhead of randomly required object instances I don't really want or need and I'm not going to create a dummy IVisual instance just to draw something on a bitmap. This just has a horrible code smell to it.

Sooo: Rendering a Avalonia.Media.Geometry (created with Geometry.Parse() for example) onto a Avalonia.Media.Bitmap. How are you actually supposed to do it?

Answer 1

void RenderToFile(Geometry geometry, Brush brush, string path)
{
    var control = new DrawingPresenter()
    {
        Drawing = new GeometryDrawing
        {
            Geometry = geometry, Brush = brush,
        },
        Width = geometry.Bounds.Right,
        Height = geometry.Bounds.Bottom
    };

    RenderToFile(control, path);
}

void RenderToFile(Control target, string path)
{
    var pixelSize = new PixelSize((int) target.Width, (int) target.Height);
    var size = new Size(target.Width, target.Height);
    using (RenderTargetBitmap bitmap = new RenderTargetBitmap(pixelSize, new Vector(96, 96)))
    {
        target.Measure(size);
        target.Arrange(new Rect(size));
        bitmap.Render(target);
        bitmap.Save(path);
    }
}