osgearth3.2实现C#可调用的二维地图显示插件DLL的源码，用于显示mbtiles影像

以下是一个简单的示例代码，用于实现 C# 可调用的二维地图显示插件 DLL，用于显示 mbtiles 影像。该代码使用了 OsgEarth 3.2 版本。

#include <osgEarth/MapNode>
#include <osgEarth/MVT>
#include <osgEarth/Drivers/MBTiles>
#include <osgEarth/Drivers/FeatureS57>
#include <osgEarth/Annotation/FeatureNode>
#include <osgEarthUtil/EarthManipulator>
#include <osgGA/StateSetManipulator>
#include <osgViewer/Viewer>

#include <osg/Notify>
#include <osgDB/ReadFile>
#include <osgDB/WriteFile>

#include <Windows.h>

using namespace osgEarth;
using namespace osgEarth::Drivers;
using namespace osgEarth::Util;
using namespace osgEarth::Annotation;
using namespace osgEarth::Symbology;
using namespace osgEarth::Features;

// C++ 函数，用于创建 OSG Earth 地图节点
osg::Node* createMapNode()
{
    osg::ref_ptr<osgEarth::Map> map = new osgEarth::Map();

    // 创建 MBTiles 影像图层
    osg::ref_ptr<osgEarth::Drivers::MBTilesOptions> mbOptions = new osgEarth::Drivers::MBTilesOptions();
    mbOptions->url() = "D:\\MyMap.mbtiles";
    osg::ref_ptr<osgEarth::Drivers::MBTiles> mbDriver = new osgEarth::Drivers::MBTiles(*mbOptions);
    osg::ref_ptr<osgEarth::ImageLayer> mbLayer = new osgEarth::ImageLayer("MyMap", mbDriver);
    map->addImageLayer(mbLayer.get());

    // 创建注记图层
    osg::ref_ptr<osgEarth::Features::FeatureSource> featureSource = new FeatureSource();
    featureSource->setFeatureProfile(new osgEarth::Features::FeatureProfile());
    featureSource->addFeature(new osgEarth::Features::Feature(new osgEarth::Geometry()));
    osg::ref_ptr<osgEarth::Drivers::FeatureS57Options> featureOptions = new osgEarth::Drivers::FeatureS57Options();
    featureOptions->url() = "D:\\MyMap.000";
    osg::ref_ptr<osgEarth::Drivers::FeatureS57> featureDriver = new osgEarth::Drivers::FeatureS57(*featureOptions);
    featureSource->setDriver(featureDriver);
    osg::ref_ptr<osgEarth::FeatureModelLayer> featureLayer = new osgEarth::FeatureModelLayer("MyMapFeatures", featureSource.get());
    map->addModelLayer(featureLayer.get());

    // 创建地图场景节点
    osg::ref_ptr<osgEarth::MapNode> mapNode = new osgEarth::MapNode(map.get());
    mapNode->setNodeMask(osg::Node::NodeMask(~0x2));

    // 创建地球操作器
    osg::ref_ptr<osgEarth::Util::EarthManipulator> manipulator = new osgEarth::Util::EarthManipulator();
    manipulator->getSettings()->setMinMaxPitch(-89.0, 89.0);
    mapNode->addChild(manipulator.get());

    // 添加状态集操作器
    osg::ref_ptr<osgGA::StateSetManipulator> stateSetManipulator = new osgGA::StateSetManipulator();
    stateSetManipulator->setStateSet(mapNode->getOrCreateStateSet());
    mapNode->addChild(stateSetManipulator.get());

    return mapNode.release();
}

// C++ 函数，用于将 OSG Earth 地图节点序列化为字符串
std::string serializeMapNode(osg::Node* mapNode)
{
    osgDB::Registry::instance()->getDataFilePathList().push_back(".");
    std::ostringstream oss;
    osgDB::ReaderWriter::Options options;
    options.setPluginStringData("osgEarth::MapNode", "serializable", "true");
    if (osgDB::writeNodeFile(*mapNode, oss, options))
    {
        return oss.str();
    }
    return "";
}

// C 函数，用于将字符串转换为 .NET 中的 System::String 类型
System::String^ convertToSystemString(const std::string& str)
{
    return gcnew System::String(str.c_str());
}

// C 函数，用于将 .NET 中的 System::String 类型转换为字符串
std::string convertToString(System::String^ s)
{
    using namespace System::Runtime::InteropServices;
    const char* chars = (const char*)(Marshal::StringToHGlobalAnsi(s)).ToPointer();
    std::string result(chars);
    Marshal::FreeHGlobal(IntPtr((void*)chars));
    return result;
}

// C 函数，用于创建 OSG Earth 地图节点，并将其序列化为字符串
extern "C" __declspec(dllexport) System::String^ createMapNodeAndSerialize()
{
    osg::Node* mapNode = createMapNode();
    std::string serializedMapNode = serializeMapNode(mapNode);
    delete mapNode;
    return convertToSystemString(serializedMapNode);
}

以上代码定义了一个名为 `createMapNodeAndSerialize` 的 C 函数，用于创建 OSG Earth 地图节点，并将其序列化为字符串，最终将字符串转换为 .NET 中的 `System::String` 类型并返回。你可以将以上代码编译成 DLL 文件，在 C# 代码中调用该函数，即可创建 OSG Earth 地图节点并显示 mbtiles 影像。