OSG添加回调更新

class CB : public osg::NodeCallback
{
    virtual void operator()(osg::Node* node, osg::NodeVisitor* nv)
    {
        osgEarth::Annotation::ImageOverlay* overlay = dynamic_cast<osgEarth::Annotation::ImageOverlay*>(node);
        overlay->getLowerLeft();
        overlay->setCorners(overlay->getLowerLeft() + osg::Vec2(0, 0.0001),
            overlay->getLowerRight() + osg::Vec2(0, 0.0001),
            overlay->getUpperLeft() + osg::Vec2(0, 0.0001),
            overlay->getUpperRight() + osg::Vec2(0, 0.0001));
        traverse(node, nv);
    }
};

osgEarth::Annotation::ImageOverlay* overlay = new osgEarth::Annotation::ImageOverlay(mapNode);
        overlay->setImage(image);
        //overlay->setBounds(Bounds(-100, 30, -90, 40));
        overlay->setCorners(lonlat, lonlat+osg::Vec2d(1 * width/height, 0),
            lonlat + osg::Vec2d(0, 1), 
            lonlat + osg::Vec2d(1* width / height, 1));
        overlay->addUpdateCallback(new CB());