OpenCV4 can't initialize GTK backend

#include <opencv2/opencv.hpp>
#include <raspicam_cv.h>
#include <iostream>

using namespace std;
using namespace cv;
using namespace raspicam;

Mat frame;
void Setup (int argc, char **argv, RaspiCam_Cv &Camera)
{
    Camera.set ( CAP_PROP_FRAME_WIDTH,  ( "-w",argc,argv,360 ) );
    Camera.set ( CAP_PROP_FRAME_HEIGHT,  ( "-h",argc,argv,240 ) );
    Camera.set ( CAP_PROP_BRIGHTNESS, ( "-br",argc,argv,50 ) );
    Camera.set ( CAP_PROP_CONTRAST ,( "-co",argc,argv,50 ) );
    Camera.set ( CAP_PROP_SATURATION,  ( "-sa",argc,argv,50 ) );
    Camera.set ( CAP_PROP_GAIN,  ( "-g",argc,argv ,50 ) );
    Camera.set ( CAP_PROP_FPS,  ( "-fps",argc,argv,0));
}    
int main(int argc, char **argv)
{
    RaspiCam_Cv Camera;
    Setup(argc, argv, Camera);
    cout<<"Connecting to Camera"<<endl;
    if(!Camera.open())
    {
       cout<<"Failed to connect";
       return -1;   
    }
    cout<<"Camera ID= "<<Camera.getId()<<endl;
    Camera.grab();
    Camera.retrieve(frame);
    
    imshow("frame", frame);
    waitKey();
    return 0;
}

error: Connecting to Camera Camera ID= 00000000b7f66138 No protocol specified Unable to init server: Could not connect: Connection refused terminate called after throwing an instance of 'cv::Exception' what(): OpenCV(4.5.0-pre) /home/pi/opencv/opencv/modules/highgui/src/window_gtk.cpp:624: error: (-2:Unspecified error) Can't initialize GTK backend in function 'cvInitSystem'

Aborted

(program exited with code: 134)