创建skiasharp camera overlay xamarin ios

using SkiaSharp;
using SkiaSharp.Views.iOS;
using UIKit;

public class CameraOverlayView : SKCanvasView
{
    public CameraOverlayView(CGRect frame) : base(frame)
    {
        // 设置视图的背景颜色为透明
        BackgroundColor = UIColor.Clear;
    }

    protected override void OnPaintSurface(SKPaintSurfaceEventArgs e)
    {
        base.OnPaintSurface(e);

        // 获取绘图上下文
        SKSurface surface = e.Surface;
        SKCanvas canvas = surface.Canvas;

        // 清空画布
        canvas.Clear();

        // 绘制覆盖层的图形
        using (SKPaint paint = new SKPaint())
        {
            paint.Color = SKColors.Red;
            paint.Style = SKPaintStyle.Fill;

            // 绘制一个红色的矩形
            canvas.DrawRect(new SKRect(100, 100, 200, 200), paint);
        }
    }
}

using AVFoundation;
using UIKit;

public class CameraViewController : UIViewController
{
    private AVCaptureSession captureSession;
    private AVCaptureVideoPreviewLayer previewLayer;

    public override void ViewDidLoad()
    {
        base.ViewDidLoad();

        // 创建相机预览视图
        var cameraOverlayView = new CameraOverlayView(View.Bounds);

        // 创建相机设备
        var cameraDevice = AVCaptureDevice.GetDefaultDevice(AVMediaTypes.Video);

        // 创建相机输入
        var cameraInput = AVCaptureDeviceInput.FromDevice(cameraDevice);

        // 创建相机输出
        var cameraOutput = new AVCaptureVideoDataOutput();

        // 设置相机输出的委托
        cameraOutput.SetSampleBufferDelegate(new CameraOutputDelegate(cameraOverlayView), DispatchQueue.MainQueue);

        // 创建捕捉会话
        captureSession = new AVCaptureSession();

        // 将相机输入和输出添加到捕捉会话中
        captureSession.AddInput(cameraInput);
        captureSession.AddOutput(cameraOutput);

        // 创建相机预览图层
        previewLayer = new AVCaptureVideoPreviewLayer(captureSession)
        {
            Frame = View.Bounds,
            VideoGravity = AVLayerVideoGravity.ResizeAspectFill
        };

        // 将相机预览图层添加到视图中
        View.Layer.AddSublayer(previewLayer);

        // 将相机覆盖层添加到视图中
        View.AddSubview(cameraOverlayView);

        // 开始捕捉会话
        captureSession.StartRunning();
    }

    public override void ViewWillDisappear(bool animated)
    {
        base.ViewWillDisappear(animated);

        // 停止捕捉会话
        captureSession?.StopRunning();
    }
}

public class CameraOutputDelegate : AVCaptureVideoDataOutputSampleBufferDelegate
{
    private readonly CameraOverlayView cameraOverlayView;

    public CameraOutputDelegate(CameraOverlayView cameraOverlayView)
    {
        this.cameraOverlayView = cameraOverlayView;
    }

    public override void DidOutputSampleBuffer(AVCaptureOutput captureOutput, CMSampleBuffer sampleBuffer, AVCaptureConnection connection)
    {
        // 在这里可以对相机输出的图像进行处理
        // 例如，可以使用SkiaSharp在cameraOverlayView上绘制图形
        cameraOverlayView.SetNeedsDisplay();
    }
}