仅当按下ESC，空格键或Enter键时，VideoFrame才会出现OpenCV c ++

Question

I am kind of an intermediate in Computer Vison and fairly proficient in opencv python however coming to c++ i am facing problems in just selecting ROI from Video feed and displaying the cropped feed .My code looks like this.

#include "opencv2/highgui.hpp"
 #include "opencv2/imgproc.hpp"
 #include "opencv2/objdetect/objdetect.hpp"
  #include "opencv2/tracking.hpp"
#include "iostream"
using namespace cv;
using namespace std;
 int main() {

Mat frame1;
VideoCapture cap;
cap.open(0);
cap.read(frame1);
Rect2d roi = selectROI(frame1, true);
Mat Crop = frame1(roi);

while (1) {

    cap.read(frame1);
    Crop = frame1(roi);
    if (Crop.empty()) {
        cerr << "ERROR! blank frame grabbed\n";
        break;

    }
    imshow("roi", Crop);
    int key=waitkey(0);

}
}

The code is compiling ,and the cropped window is seen however I am always in need to click enter,spacebar or esc to get the video feed.Weird?

Answer 1

So the correct version of the corrected code will look somewhat like this.Thanks for the help.

#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/objdetect/objdetect.hpp"
#include "opencv2/tracking.hpp"
#include "iostream"
using namespace cv;
using namespace std;
int main() {

Mat frame1;
VideoCapture cap;
cap.open(0);
cap.read(frame1);
 Rect2d roi = selectROI(frame1, true);
 Mat Crop = frame1(roi);

 while (1) {

cap.read(frame1);
Crop = frame1(roi);
if (Crop.empty()) {
    cerr << "ERROR! blank frame grabbed\n";
    break;

}
imshow("roi", Crop);
*int key=waitkey(1)*;

} }