void cvCalcMotionGradient(CvArr* mhi, CvArr* mask, CvArr* orientation, double delta1, double delta2, int aperture_size) {
    void *fptr;

    fptr = dlsym(_Chcv_handle, "cvCalcMotionGradient_chdl");
    if(fptr == NULL) {
        fprintf(_stderr, "Error: %s(): dlsym(): %s\n", __func__,  dlerror());
        return;
    }
    dlrunfun(fptr, NULL, cvCalcMotionGradient, mhi, mask, orientation, delta1, delta2, aperture_size);
}
