OpenCvSharp で Web カメラから動画を保存

CaptureIO.cs

using OpenCvSharp;
using OpenCvSharp.CPlusPlus;
using System;

namespace OpenCvSharpSample.Samples
{
    public class CaptureIO
    {

        public static void CameraSave(int cameraId, int fps, int second, bool putText = true)
        {
            var frameSize = new Size(640, 480);
            int frameCount = fps * second;

            using (var writer = new VideoWriter("output.avi", FourCC.DIVX, fps, frameSize))
            using (var capture = new VideoCapture(cameraId))
            using (var window = new Window("Capture #" + cameraId))
            {

                if (!capture.IsOpened())
                {
                    throw new InvalidOperationException("カメラが開けませんでした。");
                }

                try
                {
                    Mat mat = new Mat();

                    var textPoint = new CvPoint(frameSize.Width - 410, frameSize.Height - 10);
                    var textFontFace = FontFace.HersheyComplexSmall;
                    var textColor = new CvColor(200, 0, 50);

                    capture.FrameHeight = frameSize.Height;
                    capture.FrameWidth = frameSize.Width;

                    while (frameCount-- > 0 && Cv2.WaitKey(1000 / fps) < 0)
                    {
                        capture.Read(mat);
                        if (putText)
                        {
                            mat.PutText(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss:fff K"), textPoint, textFontFace, 1, textColor);
                        }
                        window.ShowImage(mat);
                        writer.Write(mat);
                    }
                }
                catch (OpenCVException e)
                {
                    throw new InvalidOperationException("読み込んだ画像を表示できませんでした。", e);
                }
            }
        }
    }
}