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(400, 200, 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.

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");
}