Mat opencv to NSArray IOS

I had this function, but I need to return and NSArray.

+ (NSArray *)_grayFrom_std:(Mat)source {
    cout << "-> grayFrom ->";

    Mat result;
    Mat result_std;
    cvtColor(source, result, CV_BGR2GRAY);

    Scalar m, std;
    meanStdDev(result, m, std);

    divide(result, 255, result_std);
    subtract(result_std, m, result_std);
    divide(result_std, std, result_std);


    return array;
}