Simple OpenCV video input/output sample

This short piece of code below captures a frame from a web cam and shows it in a window. Some simple transformations can be applied.

#include 
#include 

int main(void)
{
	//we assume, that there is only one camera
	CvCapture* capture= cvCaptureFromCAM(-1);

	IplImage* img;

	int loop;
	while(loop++<100)
	{
		cvGrabFrame(capture); // capture a frame
		img=cvRetrieveFrame(capture,1); // retrieve the captured frame

		// get the properties of the image
		int width     = img->width;
		int height    = img->height;
		int nchannels = img->nChannels;
		int step      = img->widthStep;

		// setup the pointer to access image data
		uchar *data = ( uchar* )img->imageData;

		int i, j,  value;
		int Rin, Gin, Bin;

		int Rout, Gout, Bout;

		for( i = 0 ; i < height ; i++ ) {
			for( j = 0 ; j < width ; j++ ) {

				Rin = data[i*step + j*nchannels + 0];
				Gin = data[i*step + j*nchannels + 1];
				Bin = data[i*step + j*nchannels + 2];

				//------ begin image maniupulation ------

				//one-to-one mapping
				//Rout=Rin;Gout=Gin;Bout=Bin;

				//grayscale conversion
				//Rout = Gout = Bout = ( Rin + Gin + Bin ) / 3;

				//some black and white thresholding
				Rout = Gout = Bout = ( Rin + Gin + Bin ) > 3*255/2 ? 255: 0;


				//------ end image maniupulation ------
				data[i*step + j*nchannels + 0] = Rout;
				data[i*step + j*nchannels + 1] = Gout;
				data[i*step + j*nchannels + 2] = Bout;
			}
		}
		cvShowImage("video output", img);
		cvWaitKey(20);
	}

	cvReleaseCapture(&capture);

	return 0;
}

The code is simply compiled with:

gcc -Wall highgui_test.c -o highgui_test -lcv -I /usr/include/opencv/ -lhighgui