How do I capture image from webcam and save it

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C++

Hello everybody, I'm trying to open webcam, catch a still image and save it into a specific directory.
the webcam opens and the image is saved, but I always get a black image.
I'm using c++ (cv.h and highgui.h)
Note that the webcam is working well using another programs, and also I've tried using another webcam, but got the same problem.
anyone can help please?!

What I have tried:

#include "cv.h"
#include <highgui.h>
#include "stdio.h"
#include <iostream> 
#include <time.h>


using  namespace  std;
void sleep(clock_t delayms);


int main(int argc, char* argv[])
 {

	int logincounter = 3;

	CvCapture* cptMyCam;
	cptMyCam = cvCreateCameraCapture(-1);//get the default cam

	//initializing
	IplImage* frame = cvCreateImage(cvSize(640, 480), IPL_DEPTH_8U, 1);

	if (cptMyCam == NULL)
	{
		exit(0);
	}

	cvNamedWindow("WebCam", 0);

	int counter = 1;
	while (-1)
	{
		if (cvGrabFrame(cptMyCam) == 0)//grabe a frame from the cam
		{
			cout << "Could not Capture";
			break;
		}
		counter--;

		frame = cvRetrieveFrame(cptMyCam);

		cvShowImage("WebCam", frame);//display the grabbed fram	
	

		while (logincounter>0)
		{

			if (counter == 0)
			{
				counter = 4;
				sleep(4000);
				cvSaveImage("C:\\FromCam\\image.jpeg", frame);//saving the captured image
				cvDestroyWindow("WebCam");
           }
}
}
}