C# Emgu BackgroundSubtractorMOG2返回黑色图像

using Emgu.CV;
using Emgu.CV.CvEnum;
using Emgu.CV.Structure;
using System;

class Program
{
    static void Main(string[] args)
    {
        // 读取视频流或图像
        VideoCapture capture = new VideoCapture(0); // 0 表示默认摄像头
        if (!capture.IsOpened)
        {
            Console.WriteLine("无法打开摄像头");
            return;
        }

        Mat frame = new Mat();
        BackgroundSubtractorMOG2 bgSubtractor = new BackgroundSubtractorMOG2();

        while (true)
        {
            capture.Read(frame);
            if (frame.Empty)
                break;

            // 应用背景减除
            Mat foregroundMask = new Mat();
            bgSubtractor.Apply(frame, foregroundMask);

            // 显示结果
            CvInvoke.Imshow("Foreground Mask", foregroundMask);

            // 按 ESC 键退出
            if (CvInvoke.WaitKey(30) == 27)
                break;
        }

        capture.Dispose();
        CvInvoke.DestroyAllWindows();
    }
}