GDAL线面互转换

最近因为项目需要，需做GDAL线面互转的功能，查阅部分资料完成，下面把核心部分的代码贴出来，留个记录，也欢迎大家提问题指正完善。

/*
* @brief ConvertPolygonToPolyline        转换面为线
* @param[in] OGRGeometry* polygon        要转换的面
* @return OGRGeometry*            　　　　转换成功后的线
* @author 
* @date 
* @note 2015年11月04日 小八创建；
*/
OGRGeometry* FeatureLayerOperator::ConvertPolygonToPolyline(OGRGeometry* polygon)
{
    // 线生成
    OGRwkbGeometryType sourceGeometryType=polygon->getGeometryType();
    sourceGeometryType=wkbFlatten(sourceGeometryType);

    OGRwkbGeometryType targetGeometryType;
    switch(sourceGeometryType)
    {
        case OGRwkbGeometryType::wkbPolygon:
            {
                OGRPolygon* pOGRPolygon=(OGRPolygon*) polygon;
                int innerCount=pOGRPolygon->getNumInteriorRings();
                if(innerCount==0)
                {
                    targetGeometryType = OGRwkbGeometryType::wkbLineString;
                    OGRLineString* pOGRLineString=(OGRLineString*)OGRGeometryFactory::createGeometry(targetGeometryType);

                    OGRLinearRing* pOGRLinearRing = pOGRPolygon->getExteriorRing();
                    int pointCount=pOGRLinearRing->getNumPoints();
                    double x=0; double y=0;
                    for(int i=0;i<pointCount;i++)
                    {    
                        x=pOGRLinearRing->getX(i);
                        y=pOGRLinearRing->getY(i);
                        pOGRLineString->addPoint(x,y);
                    }

                    return pOGRLineString;
                }    
                else
                {
                    targetGeometryType = OGRwkbGeometryType::wkbMultiLineString;
                    OGRMultiLineString* pOGRMultiLineString=(OGRMultiLineString*)OGRGeometryFactory::createGeometry(targetGeometryType);
                    
                    // 添加外环
                    　　OGRLineString ogrLineString;
                    OGRLinearRing* pOGRLinearRing = pOGRPolygon->getExteriorRing();
                    int pointCount=pOGRLinearRing->getNumPoints();
                    double x=0; double y=0;
                    for(int i=0;i<pointCount;i++)
                    {    
                        x=pOGRLinearRing->getX(i);
                        y=pOGRLinearRing->getY(i);
                        ogrLineString.addPoint(x,y);
                    }
                    pOGRMultiLineString->addGeometry(&ogrLineString);
                    
                    for(int i=0;i<innerCount;i++)
                    {
                        // 添加内环
                        OGRLineString ogrLineString0;
                        OGRLinearRing* pOGRLinearRing0 = pOGRPolygon->getInteriorRing(i);
                        int pointCount=pOGRLinearRing0->getNumPoints();
                        double x=0; double y=0;
                        for(int i=0;i<pointCount;i++)
                        {    
                            x=pOGRLinearRing0->getX(i);
                            y=pOGRLinearRing0->getY(i);
                            ogrLineString0.addPoint(x,y);
                        }
                        pOGRMultiLineString->addGeometry(&ogrLineString0);
                    }

                    return pOGRMultiLineString;
                }
            }
        case OGRwkbGeometryType::wkbMultiPolygon:
            {
                targetGeometryType = OGRwkbGeometryType::wkbMultiLineString;
                OGRMultiLineString* pOGRMultiLineString=(OGRMultiLineString*)OGRGeometryFactory::createGeometry(targetGeometryType);

                OGRGeometryCollection* pOGRPolygons=(OGRGeometryCollection*) polygon;
                int geometryCount=pOGRPolygons->getNumGeometries();

                for(int i=0;i<geometryCount;i++)
                {
                    OGRGeometry* pOGRGeo=ConvertPolygonToPolyline(pOGRPolygons->getGeometryRef(i));
                    pOGRMultiLineString->addGeometry(pOGRGeo);
                }

                return pOGRMultiLineString;
            }
        default:
            return NULL;
    }

    return NULL;
}

/*
* @brief ConvertPolylineToPolygon        转换线为面
* @param[in] OGRGeometry* polygon        要转换的面
* @return OGRGeometry*            　　　　转换成功后的线
* @author 
* @date 
* @note 2015年11月04日 小八创建；
*/
OGRGeometry* FeatureLayerOperator::ConvertPolylineToPolygon(OGRGeometry* polyline)
{
    // 线生成
    OGRwkbGeometryType sourceGeometryType=polyline->getGeometryType();
    sourceGeometryType=wkbFlatten(sourceGeometryType);

    OGRwkbGeometryType targetGeometryType;
    switch(sourceGeometryType)
    {
    case OGRwkbGeometryType::wkbLineString:
        {
            OGRLineString* pOGRLineString=(OGRLineString*) polyline;
            targetGeometryType = OGRwkbGeometryType::wkbPolygon;

            OGRPolygon* pOGRPolygon=(OGRPolygon*)OGRGeometryFactory::createGeometry(targetGeometryType);

            OGRLinearRing pOGRLinearRing;
            int pointCount=pOGRLineString->getNumPoints();
            double x=0; double y=0;
            for(int i=0;i<pointCount;i++)
            {    
                x=pOGRLineString->getX(i);
                y=pOGRLineString->getY(i);
                pOGRLinearRing.addPoint(x,y);
            }
            pOGRLinearRing.closeRings();
            pOGRPolygon->addRing(&pOGRLinearRing);
            return pOGRPolygon;
        }
    case OGRwkbGeometryType::wkbMultiLineString:
        {
            targetGeometryType = OGRwkbGeometryType::wkbMultiPolygon;
            OGRMultiPolygon* pOGRMultiPolygon=(OGRMultiPolygon*)OGRGeometryFactory::createGeometry(targetGeometryType);

            OGRGeometryCollection* pOGRPolylines=(OGRGeometryCollection*)polyline;
            int geometryCount=pOGRPolylines->getNumGeometries();

            for(int i=0;i<geometryCount;i++)
            {
                OGRGeometry* pOGRGeo=ConvertPolylineToPolygon(pOGRPolylines->getGeometryRef(i));
                pOGRMultiPolygon->addGeometry(pOGRGeo);
            }

            return pOGRMultiPolygon;
        }
    default:
        return NULL;
    }

    return NULL;
}