从鼠标获得矩形

getRectFromMouse.cpp

cv::Rect target;
bool drawing_box = false;
bool gotBB = false;

// bounding box mouse callback
void mouseHandler(int event, int x, int y, int flags, void *param) {
    switch( event ){
    case CV_EVENT_MOUSEMOVE:
        if (drawing_box){
            target.width = x-target.x;
            target.height = y-target.y;
        }
        break;
    case CV_EVENT_LBUTTONDOWN:
        drawing_box = true;
        target = cv::Rect( x, y, 0, 0 );
        break;
    case CV_EVENT_LBUTTONUP:
        drawing_box = false;
        if( target.width < 0 ){
            target.x += target.width;
            target.width *= -1;
        }
        if( target.height < 0 ){
            target.y += target.height;
            target.height *= -1;
        }
        gotBB = true;
        break;
    }
}

void getRoi(VideoCapture capture) {
    cvNamedWindow("Tracking", 0);
    cvSetMouseCallback("Tracking", mouseHandler, NULL);
    Mat frame,first,grayImg;
    capture >> frame;
    frame.copyTo(first);
    while(!gotBB)
    {
        first.copyTo(frame);
        rectangle(frame,target,Scalar(255,0,0),2);
        imshow("Tracking", frame);
        if (cvWaitKey(20) == 27)
            return;
    }
    cvSetMouseCallback("Tracker", NULL, NULL );
}