cvtColor(src, hsv, CV_BGR2HSV);
    inRange(hsv,Scalar(0,50,40), Scalar(10,255,255),thr1); //upper red range of hue cylinder
    inRange(hsv,Scalar(165,50,40), Scalar(179,255,255),thr2);// lower red range of hue cylinder
    thr1+=thr2; // Red pixels.