OGRMultiPolygon使用范例

最近在做OGRMultiPolygon相关开发的时候，遇到了新建OGRMultiPolygon对象无法正确释放的问题，后来找到示例代码，发现该对象不能直接new，以下为错误代码和正确代码的示例。

    /*********error code*********
    OGRMultiPolygon* pmp = new OGRMultiPolygon;
    delete pmp;
    pmp = nullptr;
    *********error code*********/

    //蓝色多边形
    char* szWKT_1 = "POLYGON ((113.885 22.6815, 113.9425 22.6585, 113.91 22.7, 113.885 22.6815))";
    //橙色多边形
    char* szWKT_2 = "POLYGON ((113.91 22.7, 113.9425 22.6585, 113.9675 22.689, 113.91 22.7))";
    OGRGeometry* pGeom_1 = NULL;
    OGRGeometry* pGeom_2 = NULL;
    OGRGeometryFactory::createFromWkt(&szWKT_1, NULL, &pGeom_1);
    OGRGeometryFactory::createFromWkt(&szWKT_2, NULL, &pGeom_2);
    OGRMultiPolygon* pMultiPolygon = (OGRMultiPolygon*)OGRGeometryFactory::createGeometry(wkbMultiPolygon);
    pMultiPolygon->addGeometryDirectly(pGeom_1);
    pMultiPolygon->addGeometryDirectly(pGeom_2);
    //用Buffer替代Union，缓冲距离设置为0
    //pUnion为紫色多边形
    OGRGeometry* pUnion = pMultiPolygon->Buffer(0);

    delete pMultiPolygon;
    pMultiPolygon = nullptr;

    return 0;