Get a specific pixel coordinates where your mouse on （cc)

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


IplImage* src=0;

void on_mouse( int event, int x, int y, int flags, void* ustc)
{
    CvFont font;
    cvInitFont(&font, CV_FONT_HERSHEY_SIMPLEX, 0.5, 0.5, 0, 1, CV_AA);
    if( event == CV_EVENT_LBUTTONDOWN )
    {
        CvPoint pt = cvPoint(x,y);
        char temp[16];
        sprintf(temp,"(%d,%d)",pt.x,pt.y);
        cvPutText(src,temp, pt, &font, cvScalar(255, 255, 255, 0));
        cvCircle( src, pt, 2,cvScalar(255,0,0,0) ,CV_FILLED, CV_AA, 0 );
        cvShowImage( "src", src );
    }
}

int main()
{
    src=cvLoadImage("lena.jpg",1);
    cvNamedWindow("src",1);
    cvSetMouseCallback( "src", on_mouse, 0 );

    cvShowImage("src",src);

    cvWaitKey(0);
    cvDestroyAllWindows();
    cvReleaseImage(&src);

    return 0;
}