CvSeq* cvConvexHull2(CvArr* input, void* hull_storage, int orientation, int return_points) {
    void *fptr;
    CvSeq*retval;

    fptr = dlsym(_Chcv_handle, "cvConvexHull2_chdl");
    if(fptr == NULL) {
        fprintf(_stderr, "Error: %s(): dlsym(): %s\n", __func__,  dlerror());
        return NULL;
    }
    dlrunfun(fptr, &retval, cvConvexHull2, input, hull_storage, orientation, return_points);
    return retval;
}
