#dotnet – Display the 🎦 camera feed in a WinForm using #OpenCV and #net5

Hi !

Back on the Windows Forms days, cameras were tricky. We didn’t have a lot of libraries to work, and they usually require some extra work to handle unexpected errors. With Net 5 and OpenCVSharp, we can create a simple WebCam viewer like this one.

Let’s start with a [Take a Photo] Windows Form app. This App have a PictureBox and a Button, and it’s all connected with these lines.

	using System;
	using System.Windows.Forms;
	using OpenCvSharp;
	namespace Demo03_WinForm
	{
	public partial class Form1 : Form
	{
	private VideoCapture _capture;
	private Mat _image;
	public Form1()
	{
	InitializeComponent();
	}
	private void Form1_Load(object sender, EventArgs e)
	{
	_capture = new VideoCapture(0);
	_image = new Mat();
	}
	private void button1_Click(object sender, EventArgs e)
	{
	_capture.Read(_image);
	if (_image.Empty()) return;
	pictureBox1.Image = OpenCvSharp.Extensions.BitmapConverter.ToBitmap(_image);
	}
	}
	}

view raw net5opencvtakephoto.cs hosted with ❤ by GitHub

As you can see it’s super simple, and the main lesson to learn here is on line 27, when we need to convert the OpenCV Mat object to a standard Bitmap to be used on a PictureBox.

We can some more features, like the one in the animation before

• Start / Stop Camera Preview
• Calculate FPS
• Add Canny effect

with the following lines

	using System;
	using System.Threading;
	using System.Windows.Forms;
	using OpenCvSharp;
	using OpenCvSharp.Extensions;
	using Point = OpenCvSharp.Point;
	using Size = OpenCvSharp.Size;
	namespace Demo04_WinForm
	{
	public partial class Form1 : Form
	{
	private bool _run = false;
	private bool _canny = false;
	private VideoCapture _capture;
	private Mat _image;
	private Thread _cameraThread;
	private bool _fps = false;
	public Form1()
	{
	InitializeComponent();
	Load += Form1_Load;
	Closed += Form1_Closed;
	}
	private void Form1_Closed(object sender, EventArgs e)
	{
	_cameraThread.Interrupt();
	_capture.Release();
	}
	private void btnStart_Click(object sender, EventArgs e)
	{
	_run = true;
	}
	private void btnStop_Click(object sender, EventArgs e)
	{
	_run = false;
	}
	private void btnCanny_Click(object sender, EventArgs e)
	{
	_canny = !_canny;
	}
	private void buttonFPS_Click(object sender, EventArgs e)
	{
	_fps = !_fps;
	}
	private void Form1_Load(object sender, EventArgs e)
	{
	_capture = new VideoCapture(0);
	_image = new Mat();
	_cameraThread = new Thread(new ThreadStart(CaptureCameraCallback));
	_cameraThread.Start();
	}
	private void CaptureCameraCallback()
	{
	while (true)
	{
	if (!_run) continue;
	var startTime = DateTime.Now;
	_capture.Read(_image);
	if (_image.Empty()) return;
	var imageRes = new Mat();
	Cv2.Resize(_image, imageRes, new Size(320, 240));
	var newImage = imageRes.Clone();
	if (_canny)
	Cv2.Canny(imageRes, newImage, 50, 200);
	if (_fps)
	{
	var diff = DateTime.Now – startTime;
	var fpsInfo = $"FPS: Nan";
	if (diff.Milliseconds > 0)
	{
	var fpsVal = 1.0 / diff.Milliseconds * 1000;
	fpsInfo = $"FPS: {fpsVal:00}";
	}
	Cv2.PutText(imageRes, fpsInfo, new Point(10, 20), HersheyFonts.HersheyComplexSmall, 1, Scalar.White);
	}
	var bmpWebCam = BitmapConverter.ToBitmap(imageRes);
	var bmpEffect = BitmapConverter.ToBitmap(newImage);
	pictureBoxWebCam.Image = bmpWebCam;
	pictureBoxEffect.Image = bmpEffect;
	}
	}
	}
	}

view raw net5opencvlivecamera.cs hosted with ❤ by GitHub

Less than 100 lines of code to do some camera image processing in WinForms!

That’s all for today!

References

• OpenCVSharp, https://github.com/shimat/opencvsharp
• Wikipedia, Canny Edge Detector
• OpenCV, Canny tutorial
• openCV, FAST tutorial
• Wikipedia, FAST