OpenCV 库中的 VideoCapture 类来读取视频文件进行光流法视频追踪c#

在 C# 中使用 OpenCV 库进行光流法视频追踪的方法与 C++ 中类似，只是语法上有所不同。需要使用 NuGet 包管理器安装 EmguCV 库，它是 C# 的 OpenCV 库封装。

代码示例：

using System;
using Emgu.CV;
using Emgu.CV.Structure;
using Emgu.CV.Util;
using Emgu.CV.Features2D;

namespace OpticalFlowDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            // 读取视频文件
            VideoCapture capture = new VideoCapture("test.avi");

            if (!capture.IsOpened)
            {
                Console.WriteLine("Error opening video file");
                return;
            }

            // 获取第一帧图像
            Mat prev_frame = new Mat();
            Mat next_frame = new Mat();
            capture.Read(prev_frame);

            // 转换为灰度图像
            CvInvoke.CvtColor(prev_frame, prev_frame, Emgu.CV.CvEnum.ColorConversion.Bgr2Gray);

            // 提取关键点
            VectorOfPointF prev_points = new VectorOfPointF();
            VectorOfPointF next_points = new VectorOfPointF();
            GFTTDetector detector = new GFTTDetector(100, 0.3, 7, 7, false, 0.04);
            detector.Detect(prev_frame, prev_points);

            // 进行追踪
            Mat status = new Mat();
            Mat err = new Mat();
            while (true)
            {
                // 读取下一帧图像
                capture.Read(next_frame);
                if (next_frame.IsEmpty)
                    break;

                // 转换为灰度图像
                CvInvoke.CvtColor(next_frame, next_frame, Emgu.CV.CvEnum.ColorConversion.Bgr2Gray);

                // 进行光流法追踪
                OpticalFlow.PyrLK(prev_frame, next_frame, prev_points, next_points, status, err);

                // 绘制轨迹
                PointF[] prev_points_array = prev_points.ToArray();
                PointF[] next_points_array = next_points.ToArray();
                for (int i = 0; i < prev_points_array.Length; i++)
                {
                    if (status.GetData(i)[0] == 1)
                    {
                        CvInvoke.Line(next_frame, Point.Round(prev_points_array[i]), Point.Round(next_points_array[i]), new MCvScalar(0, 255, 0), 2);
                        CvInvoke.Circle(next_frame, Point.Round(next_points_array[i]), 5, new MCvScalar(0, 0, 255), -1);
                    }
                }

                // 显示图像
                CvInvoke.Imshow("Optical Flow Tracking", next_frame);

                // 更新变量
                prev_points = next_points;
                prev_frame = next_frame.Clone();

                // 等待按键
                if (CvInvoke.WaitKey(30) == 27)
                    break;
            }

            // 释放资源
            capture.Dispose();
            CvInvoke.DestroyAllWindows();
        }
    }
}