在 SkiaSharp 中不使用 PaintSurface 事件进行绘图的最有效方法

这个的延伸question https://forums.xamarin.com/discussion/99300/is-there-a-way-to-access-a-sksurface-outside-of-the-paintsurface-event。我在用着SkiaSharp绘制形状OpenGL。大多数 WPF 代码示例建议使用SKElement控制并获取内部绘图表面的参考PaintSurface事件。我一直需要参考绘图表面，而不仅仅是在这个事件中，所以我正在使用SKBitmap and SKCanvas并将输出发送到ImageWPF 中的控制。

XAML

<Canvas x:Name="ScreenControl" />

CS

var bmp = new SKBitmap((int)ScreenControl.ActualWidth, (int)ScreenControl.ActualHeight);
var canvas = new SKCanvas(bmp);
var image = new Image
{
  Stretch = Stretch.Fill
};

canvas.DrawText("Demo", new SKPoint(20, 20), new SKPaint { TextSize = 20 });

var index = 0;
var clock = new Timer();
var wrt = bmp.ToWriteableBitmap();

image.Source = wrt;

clock.Interval = 100;
clock.Elapsed += (object sender, ElapsedEventArgs e) =>
{
  Application.Current.Dispatcher.BeginInvoke(new Action(() =>
  {
    var wrt = bmp.ToWriteableBitmap(); // Potentially slow line #1

    canvas.Clear();
    canvas.DrawText((index++).ToString(), new SKPoint(20, 20), new SKPaint { TextSize = 20 });
    image.Source = wrt;                // Potentially slow line #2
    image.InvalidateVisual();
  }));
};
clock.Start();

ScreenControl.Children.Clear();
ScreenControl.Children.Add(image);

Project

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>net5.0-windows</TargetFramework>
    <UseWPF>true</UseWPF>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="SkiaSharp.Views.WPF" Version="2.80.3-preview.18" />
  </ItemGroup>

</Project>

Question

有没有一种方法可以更快地绘制，特别是无需重新创建位图bmp.ToWriteableBitmap()并且无需每次都更改图像源image.Source = wrt？后台缓冲区或相关的东西？

你必须使用 Skia 的 SKElement：

<Grid>
    <skia:SKElement PaintSurface="OnPaintSurface" IgnorePixelScaling="True" />
</Grid>

并在 OnPaintSurface 中绘制：

    private void OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
    {
        // the the canvas and properties
        var canvas = e.Surface.Canvas;

        // make sure the canvas is blank
        canvas.Clear(SKColors.White);

        // draw some text
        var paint = new SKPaint
        {
            Color = SKColors.Black,
            IsAntialias = true,
            Style = SKPaintStyle.Fill,
            TextAlign = SKTextAlign.Center,
            TextSize = 24
        };
        var coord = new SKPoint(e.Info.Width / 2, (e.Info.Height + paint.TextSize) / 2);
        canvas.DrawText("SkiaSharp", coord, paint);
    }