Initialize a vector of Rect with some Rect objects - Opencv C++

Question

I'm working on a face tracking project with Kalman Filter. Basically, I want to store the result of my tracking application (int x, int y, int width, int heigth) on a vector of Rectangles, (i.e. each face will be stored on a Rect, then all the Rects will be stored on a vector of Rect).

The following code is what I tried to do:

Rect faceTracked(Estimated_int.at<int>(0, 0), Estimated_int.at<int>(
                1, 0), Estimated_int.at<int>(2, 0), Estimated_int.at<int>(3, 0));
        std::vector <Rect> facesVector;
        facesVector[i] = faceTracked;

Where "Estimated_int" is the result matrix (4,1) of KF. When I run this code the following error is displayed on Android Studio Logcat, then the app crashes:

11-21 17:36:43.729 10735-11321/com.example.android.ndkopencvtest1 A/libc: Fatal signal 11 (SIGSEGV), code 1, fault addr 0x0 in tid 11321 (Thread-5)

That error only happens when the statement facesVector[i] = faceTracked is called. What am I doing wrong? The entire function code is shown below:

void trackFace (Mat& frame, std::vector<Rect> faces) {
for (size_t i = 0; i < faces.size(); i++) {
    X = A * X_p;
    transpose(A, A_transpose);
    P = A * P_p * A_transpose;
    if (faces.size() > 0) {
        Mat Z = (Mat_<float>(4, 1) << faces[i].x, faces[i].y, faces[i].x + faces[i].width,
                faces[i].y + faces[i].height);
        Y = Z - H * X;
        transpose(H, H_transpose);
        S = H * P * H_transpose + R;
        invert(S, S_inverse);
        K = P * H_transpose * S_inverse;
        X_p = X + K * Y;
        Estimated = H * X_p;
        P_p = (Ident - K * H) * P;
        Mat Estimated_int = (Mat_<int>(4, 1) << cvRound(Estimated.at<float>(0, 0)), cvRound(
                Estimated.at<float>(1, 0)), cvRound(Estimated.at<float>(2, 0)), cvRound(
                Estimated.at<float>(3, 0)));
        rectangle(frame, Point((Estimated_int.at<int>(0, 0)), (Estimated_int.at<int>(1, 0))),
                  Point((Estimated_int.at<int>(2, 0)), (Estimated_int.at<int>(3, 0))),
                  Scalar(255, 255, 102, 255), 2, 8, 0);
        Rect faceTracked(Estimated_int.at<int>(0, 0), Estimated_int.at<int>(
                1, 0), Estimated_int.at<int>(2, 0), Estimated_int.at<int>(3, 0));
        std::vector <Rect> facesVector;
        facesVector[i] = faceTracked;

    }
}

}

@edit: All matrix were properly initialized on a header file. It was tested before and it is working.

Your vector has no size, also `i` is not declared, please try to make sure you're including all relevant code. — George, Nov 21 '17 at 19:55
You're assigning to the i-th element of the **empty** vector `facesVector`. Also your function doesn't produce any result — Miki, Nov 21 '17 at 20:40
@Miki I just need to store all the rectangles (faceTracked) on a vector of Rectangles (facesVector). Do you know how can I do that? — Gabriel Cambraia Soares, Nov 21 '17 at 22:07
@GabrielCambraiaSoares why not just make a `std::vector` and `push_back()` to that vector? — alkasm, Nov 22 '17 at 03:07

Initialize a vector of Rect with some Rect objects - Opencv C++

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