Hello World in CSharp

This example requires Emgu CV 1.5.0.0 and up

Hello World - Version 1

We will start by the Hello World sample, written in C#

Emgu CV 3.0

Click to view source code

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

...

String win1 = "Test Window"; //The name of the window
CvInvoke.NamedWindow(win1); //Create the window using the specific name

Mat img = new Mat(200, 400, DepthType.Cv8U, 3); //Create a 3 channel image of 400x200
img.SetTo(new Bgr(255, 0, 0).MCvScalar); // set it to Blue color

//Draw "Hello, world." on the image using the specific font
CvInvoke.PutText(
   img, 
   "Hello, world", 
   new System.Drawing.Point(10, 80), 
   FontFace.HersheyComplex, 
   1.0, 
   new Bgr(0, 255, 0).MCvScalar);
         

CvInvoke.Imshow(win1, img); //Show the image
CvInvoke.WaitKey(0);  //Wait for the key pressing event
CvInvoke.DestroyWindow(win1); //Destroy the window if key is pressed

Emgu CV 1.5

Click to view source code

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

...

//The name of the window
String win1 = "Test Window";

//Create the window using the specific name
CvInvoke.cvNamedWindow(win1);

//Create an image of 400x200 of Blue color
using (Image<Bgr, Byte> img = new Image<Bgr, byte>(400, 200, new Bgr(255, 0, 0))) 
{
   //Create the font
   MCvFont f = new MCvFont(CvEnum.FONT.CV_FONT_HERSHEY_COMPLEX, 1.0, 1.0);
   //Draw "Hello, world." on the image using the specific font
   img.Draw("Hello, world", ref f, new Point(10, 80), new Bgr(0, 255, 0));

   //Show the image
   CvInvoke.cvShowImage(win1, img.Ptr);
   //Wait for the key pressing event
   CvInvoke.cvWaitKey(0);
   //Destory the window
   CvInvoke.cvDestroyWindow(win1); 
}

The above code will create an image of 400x200 with blue background color and the text "Hello, world" in green on the foreground. The image will be displayed a window named "Test Window".

Hello World - Version 2

Showing image using cvNamedWindow is good, but Emgu CV has an event better tool for the same purpose, that is, the ImageViewer class under Emgu.CV.UI namespace.

Emgu CV 3.0

Click to view source code

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

...

//Create a 3 channel image of 400x200
using (Mat img = new Mat(200, 400, DepthType.Cv8U, 3)) 
{
   img.SetTo(new Bgr(255, 0, 0).MCvScalar); // set it to Blue color

   //Draw "Hello, world." on the image using the specific font
   CvInvoke.PutText(
      img, 
      "Hello, world", 
      new System.Drawing.Point(10, 80), 
      FontFace.HersheyComplex, 
      1.0, 
      new Bgr(0, 255, 0).MCvScalar);
   
   //Show the image using ImageViewer from Emgu.CV.UI
   ImageViewer.Show(img, "Test Window");
}

Emgu CV 2.x

Click to view source code

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

...

//Create an image of 400x200 of Blue color
using (Image<Bgr, Byte> img = new Image<Bgr, byte>(400, 200, new Bgr(255, 0, 0))) 
{
   //Create the font
   MCvFont f = new MCvFont(CvEnum.FONT.CV_FONT_HERSHEY_COMPLEX, 1.0, 1.0);

   //Draw "Hello, world." on the image using the specific font
   img.Draw("Hello, world", ref f, new Point(10, 80), new Bgr(0, 255, 0)); 
   
   //Show the image using ImageViewer from Emgu.CV.UI
   ImageViewer.Show(img, "Test Window");
}