void cvSetPostprocessFuncWin32(CvWin32WindowCallback on_postprocess) {
    void *fptr;

    fptr = dlsym(_Chhighgui_handle, "cvSetPostprocessFuncWin32_chdl");
    if(fptr == NULL) {
        fprintf(_stderr, "Error: %s(): dlsym(): %s\n", __func__,  dlerror());
        return;
    }
    dlrunfun(fptr, NULL, cvSetPostprocessFuncWin32, on_postprocess);
}