Playing with webcam in OpenCV 2.1

I have posted an article about capturing and processing image using webcam in OpenCV 1.0. Right now I'm trying to upgrade my program to use OpenCV 2.1. Some functions are different but basically most of them are similar.

I'm using Microsoft Visual C++ 2008 as the compiler and Windows Form Application. It's quite straight away. This is an example of the user interface:

Basically, there are many ways of doing this, the one that I choose is using event trigger approach. So the image will be shown every time there's a new event from the camera received by the system.

Here's the details, I assume that you are already familiar with C++, Visual C++ 2008, and installing OpenCV 2.1 in C++ 2008:

1. include all the needed include files:
   

   #include < cv.h >
   #include < cxcore.h >
   #include < highgui.h >
   

2. Declare the needed objects, to make it simple just declare them as global variables:

   // object for capturing image   
   CvCapture*  capture;

   // iplimage objects   
   IplImage*  image;
   IplImage*  procimage;
   

   // image size
   double w;
   double h;
   

   // boolean variables for flag
   bool blnCapInProgress;
   bool blnGrabImage;
   

3. Initialize the capture when the start button is clicked.
   

4. // size of the image   
   w = 640;
   h = 480;
   

   // creating the capture object, connecting it to the camera, and set the size   
   capture = cvCreateCameraCapture(0);
   cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH, w);
   cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT, h);
   

   // initialize the images and windows   
   image      = cvCreateImage(cvSize(w, h), IPL_DEPTH_8U, 3);
   procimage = cvCreateImage(cvSize(w, h), IPL_DEPTH_8U, 1);
   cvNamedWindow("continuous", CV_WINDOW_AUTOSIZE);
   cvNamedWindow("gray", CV_WINDOW_AUTOSIZE);
   

   // declaration of event handle  
   if(capture != NULL)
   {
   this->label1->Text = "ok";
   
   if (blnCapInProgress)
   {
   // stop the capture     // the capture is stopped by removing the event handler..
   Application::Idle -= gcnew EventHandler(this, &OpenCVImage::Form1::ProcessFrame);
   buttonStart->Text = "Start Capture";
   }
   else
   {
   //start the capture     // the capture is stopped by adding the event handler..
   Application::Idle += gcnew EventHandler(this, &OpenCVImage::Form1::ProcessFrame);
   buttonStart->Text = "Stop";
   }
   
   blnCapInProgress = !blnCapInProgress;        
   }
   

   
   
5. The event handler is inside the ProcessFrame function, create a function like this:

   private: System::Void ProcessFrame(System::Object^ sender, System::EventArgs^ e) {
   // query the image from the camera   
   image = cvQueryFrame(capture);
   // show the image
   if(image != NULL)
   {                   // image processing algorithm can be performed here
   cvCvtColor(image, procimage, CV_RGB2GRAY);
   cvShowImage("continuous", image);
   cvShowImage("gray", procimage);
   }
   // grab the image
   if(blnGrabImage)
   {
   cvSaveImage("image.bmp", image);
   cvShowImage("grab image", image);
   blnGrabImage = false;
   }
   }
   

6. You can grab the image simply by setting the blnGrabImage variable to true.
7. And what you can get is something like this... :D