OpenCV : How to display webcam capture in windows form application? - c++

Question

generally we display webcam or video motion in opencv windows with :
CvCapture* capture = cvCreateCameraCapture(0);
cvNamedWindow( "title", CV_WINDOW_AUTOSIZE );
cvMoveWindow("title",x,y);
while(1)
{
frame = cvQueryFrame( capture );
if( !frame )
{
break;
}
cvShowImage( "title", frame );
char c = cvWaitKey(33);
if( c == 27 )
{
break;
}
}
i tried to use pictureBox that is successful to display image in windows form with this :
pictureBox1->Image = gcnew System::Drawing::Bitmap( image->width,image->height,image->widthStep,System::Drawing::Imaging::PixelFormat::Undefined, ( System::IntPtr ) image-> imageData);
but when im trying to display captured image from video it wont works, here is the source :
CvCapture* capture = cvCreateCameraCapture(0);
while(1)
{
frame = cvQueryFrame( capture );
if( !frame )
{
break;
}
pictureBox1->Image = gcnew System::Drawing::Bitmap( frame->width,frame->height,frame->widthStep,System::Drawing::Imaging::PixelFormat::Undefined, ( System::IntPtr ) frame-> imageData);
char c = cvWaitKey(33);
if( c == 27 )
{
break;
}
}
is there anyway to use windows form instead opencv windows to show video or webcam?
or is there something wrong with my code?
thanks for your help.. :)

Answer 1

Piece of advice : use VideoInput instead of CvCapture (CvCapture is a part of highgui a library that is not intended for production use, but just for quick testing). Yes the VideoInput homepage looks strange, but the library is quite worthwhile.
Here is a quick sample for the usage of VideoInput (extracted from the VideoInput.h file):
//create a videoInput object
videoInput VI;
//Prints out a list of available devices and returns num of devices found
int numDevices = VI.listDevices();
int device1 = 0; //this could be any deviceID that shows up in listDevices
int device2 = 1; //this could be any deviceID that shows up in listDevices
//if you want to capture at a different frame rate (default is 30)
//specify it here, you are not guaranteed to get this fps though.
//VI.setIdealFramerate(dev, 60);
//setup the first device - there are a number of options:
VI.setupDevice(device1); //setup the first device with the default settings
//VI.setupDevice(device1, VI_COMPOSITE); //or setup device with specific connection type
//VI.setupDevice(device1, 320, 240); //or setup device with specified video size
//VI.setupDevice(device1, 320, 240, VI_COMPOSITE); //or setup device with video size and connection type
//VI.setFormat(device1, VI_NTSC_M); //if your card doesn't remember what format it should be
//call this with the appropriate format listed above
//NOTE: must be called after setupDevice!
//optionally setup a second (or third, fourth ...) device - same options as above
VI.setupDevice(device2);
//As requested width and height can not always be accomodated
//make sure to check the size once the device is setup
int width = VI.getWidth(device1);
int height = VI.getHeight(device1);
int size = VI.getSize(device1);
unsigned char * yourBuffer1 = new unsigned char[size];
unsigned char * yourBuffer2 = new unsigned char[size];
//to get the data from the device first check if the data is new
if(VI.isFrameNew(device1)){
VI.getPixels(device1, yourBuffer1, false, false); //fills pixels as a BGR (for openCV) unsigned char array - no flipping
VI.getPixels(device1, yourBuffer2, true, true); //fills pixels as a RGB (for openGL) unsigned char array - flipping!
}
//same applies to device2 etc
//to get a settings dialog for the device
VI.showSettingsWindow(device1);
//Shut down devices properly
VI.stopDevice(device1);
VI.stopDevice(device2);

Answer 2

The pixel format should be known when you capture images from a camera, it's very likely the format of 24-bit BGR. System::Drawing::Imaging::PixelFormat::Format24bppRgb will be the closest format but you might get weird color display. A re-arrange of the color component will solve this problem.
Actually, there are .net version opencv library available here:
http://code.google.com/p/opencvdotnet/
and here:
http://www.emgu.com/wiki/index.php/Main_Page
Hope it helps!

Answer 3

I don't know if you will like this, but you could use OpenGL to show the video stream in other windows than the ones provided with opencv. (Capture the frame and display it on a rectangle.. or something like that..)

Answer 4

Another option you might want to consider is using emgu. This is a .Net wrapper for opencv with winforms controlls.