Best way to convert from cv::Mat to NDArray [C++]?

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As the title suggest, what is the best / most efficient way to convert form an OpenCV Mat CV_8UC3 to an NDArray in C++? This is my current implementation, but I feel it can be improved. Thanks for the help


NDArray TruefaceFRVT11::mtxToNDArr(const cv::Mat& frame) {
    NDArray retArr(Shape(1, frame.channels(), frame.rows, frame.cols), m_globalCtx, false);
    std::vector<float> data;

    for (int c = 0; c < frame.channels(); ++c) {
        for (int i = 0; i < frame.rows; ++i) {
            for (int j = 0; j < frame.cols; ++j) {
                data.emplace_back(static_cast<float>(frame.data[(i * frame.rows + j) * 3 + c]));
            }
        }
    }

    retArr.SyncCopyFromCPU(data.data(), 1 * frame.channels() * frame.rows * frame.cols);
    // NDArray::WaitAll();

    return retArr;
}