序言

在一个项目中，需要输出osg仿真的图像结果，但是直接借用源码中的ScreenCaptureHandler无法实现咋指定目录下输出，且输出图像名称无法修改，默认使用按键的响应方式无法满足项目需求，在参考相关源码和帖子的基础上，以及方方的大力帮助下，有了下面的内容。
与现有网上大量内容相比，其只给出了代码，没有给出如何使用，让和我一样的超级菜鸟一头雾水。所以有了下面的内容。

a.h文件定义如下：

#pragma once
 #ifndef A_H
#define A_H
 #include <string>
#include <osgDB/WriteFile>
#include <osgViewer/ViewerEventHandlers>
 
class CScreenCapture : public osgViewer::ScreenCaptureHandler
{
public:
    int il;
    class  WriteToImageFile : public osgViewer::ScreenCaptureHandler::CaptureOperation
    {
    public:
        enum SavePolicy
        {
            OVERWRITE,
            SEQUENTIAL_NUMBER
        };
 
        WriteToImageFile(const std::string& filename, const std::string& extension, SavePolicy savePolicy = SEQUENTIAL_NUMBER) 
 
        {
            _filename = filename;
            _extension = extension;
            _savePolicy = savePolicy;
            ik = 0;
        }
 
        virtual void operator()(const osg::Image& image, const unsigned int context_id)//仿函数实现图片保存
        {
            if (!_filename.empty())
            {
        
                std::string patch = _filename+"_"+std::to_string(ik)+"." + _extension;
                osgDB::writeImageFile(image, patch); 
                ik++;
            }
        }
 
        void setFileName(const std::string &filename){
            _filename = filename;
            
        }
 
        void setSavePolicy(SavePolicy savePolicy) { _savePolicy = savePolicy; }

        SavePolicy getSavePolicy() const { return _savePolicy; }
 
    protected:
 
        WriteToImageFile& operator = (const WriteToImageFile&) { return *this; }
 
        std::string _filename;
        std::string _extension;
 
        SavePolicy _savePolicy;
 
        std::vector<unsigned int> _contextSaveCounter;

        int ik;
 
    };
    
    CScreenCapture(CaptureOperation* defaultOperation = 0, int numFrames = 1);
    virtual bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa);
    //void setFileName();
};
 
#endif  
//https://blog.csdn.net/xjujun/article/details/38986301

a.cpp如下：

/****************************************************************************
*
*
*
****************************************************************************/
 
//#include "stdafx.h"
#include "a.h"
 

CScreenCapture::CScreenCapture(CaptureOperation* defaultOperation /*= 0*/, int numFrames/* = 1*/):
ScreenCaptureHandler( defaultOperation, numFrames )
{
    il = 0;
}
 
bool CScreenCapture::handle( const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa )
{
    osgViewer::ViewerBase* viewer = dynamic_cast<osgViewer::View*>(&aa)->getViewerBase();
    if (!viewer) return false;
 
    switch(ea.getEventType())
    {
        case (osgGA::GUIEventAdapter::FRAME):
        {  
                addCallbackToViewer(*viewer);
                if (getFramesToCapture() == 0)
                {
                    setFramesToCapture(1);

                }
     
 
            break;
        }
        
        default:
            break;
    }
    return false;
}
 
//void CScreenCapture::setFileName()
//{
//  CScreenCapture::WriteToImageFile* wtf =  dynamic_cast<CScreenCapture::WriteToImageFile*>(getCaptureOperation());
//  //wtf->setFileName("11111111.jpg");
//  //wtf->setSavePolicy(wtf->SEQUENTIAL_NUMBER);
//  wtf->setFileName(std::to_string(il) + ".jpg");
//} 

用法：

....
    std::string path = "./1/IR123456789.jpg";
    osg::ref_ptr<CScreenCapture::WriteToImageFile> wfi = new CScreenCapture::WriteToImageFile(
        osgDB::getNameLessExtension(path),
        osgDB::getFileExtension(path)
 ); 
    
    osg::ref_ptr<CScreenCapture >cs = new CScreenCapture(wfi.get());
 
    viewer.addEventHandler(cs.get());
//外部控制时，使用  viewer.removeEventHandler(cs.get());//此处未测试
....

参考资料：

1. https://blog.csdn.net/xjujun/article/details/38986301
2. osg源码: D:\OSG\OSG_3.4.0\src\applications\present3D\present3D.cpp [line624]

    // add the screen capture handler
    std::string screenCaptureFilename = "screen_shot.jpg";
    while(arguments.read("--screenshot", screenCaptureFilename)) {}
    osg::ref_ptr<osgViewer::ScreenCaptureHandler::WriteToFile> writeFile = new osgViewer::ScreenCaptureHandler::WriteToFile(
        osgDB::getNameLessExtension(screenCaptureFilename),
        osgDB::getFileExtension(screenCaptureFilename) );
    osg::ref_ptr<osgViewer::ScreenCaptureHandler> screenCaptureHandler = new osgViewer::ScreenCaptureHandler(writeFile.get());
    screenCaptureHandler->setKeyEventTakeScreenShot('m');//osgGA::GUIEventAdapter::KEY_Print);
    screenCaptureHandler->setKeyEventToggleContinuousCapture('M');
    viewer.addEventHandler(screenCaptureHandler.get());