Open CV Harris Corner Detection - c++

Question

I have created a simple class to detect corners using
harris algorithm
. it is working but when I change the threshold value using trackbar and when the value is getting low (below 100) then the process is stopped.
this is my sample code.
my header file
class CornerCapturer{
struct configValues
{
int block;
int k_size;
int thre;
double k;
configValues() :block(2), k_size(3), thre(100), k(0.04){}
};
public:
static configValues conf;
void captureCorners();
static void captevent(int, void*);
Mat captureCornerPoints(int thresh, int block, int k_size, double k, Mat frame);
};
my Cpp file
void CaptureBall::detectCorners(){
CornerCapturer capt;
VideoCapture cap = capture.captureVideo();
cap.read(frame);
capt.captureCorners();
for (;;){
cap.read(frame);
capt.captevent(0, 0);
waitKey(5);
}
}
void CornerCapturer::captureCorners(){
int *t = &CornerCapturer::conf.thre;
namedWindow("Open", CV_WINDOW_AUTOSIZE);
captevent(0, 0);
createTrackbar("Thresh", "Open", t, 255, CornerCapturer::captevent);
}
void CornerCapturer::captevent(int, void*){
Mat res;
CornerCapturer cap;
res = cap.captureCornerPoints(CornerCapturer::conf.thre, CornerCapturer::conf.block, CornerCapturer::conf.k_size, CornerCapturer::conf.k, frame);
imshow("Open", res);
}
Mat CornerCapturer::captureCornerPoints(int thresh, int block, int k_size, double k, Mat f){
Mat gray, corner_detected, cnv_normal,copy;
copy = f;
cvtColor(copy, gray, COLOR_RGB2GRAY); // convert to gray image
cornerHarris(gray, corner_detected, block, k_size, k, BORDER_DEFAULT); // detect cornet points
normalize(corner_detected, cnv_normal, 0, 255, NORM_MINMAX, CV_32FC1, Mat()); // normalize image
for (int j = 0; j < cnv_normal.rows; j++)
{
for (int i = 0; i < cnv_normal.cols; i++)
{
if ((int)cnv_normal.at<float>(j, i) > thresh)
{
circle(copy, Point(i, j), 8, Scalar(120), 2, 8, 0); // put points
}
}
}
return copy;
}
i used OpenCV library for track corners