关于窗口截图的问题

Question

我的代码是这样的
CWnd *cwnd=FromHandle(hWnd);这个是要被截图的窗口句柄
CDC *robetDC=this->GetDC();这个是显示图片的窗口DC
CDC *gameDC=cwnd->GetDC();
CDC *gameMDC=new CDC;
gameMDC->CreateCompatibleDC(gameDC);
CBitmap *gameMap=new CBitmap;
gameMap->CreateCompatibleBitmap(gameMDC,100,100);
gameMDC->SelectObject(gameMap);
robetDC->BitBlt(50,50,50,50,gameMDC,20,20,SRCCOPY);
gameMap->DeleteObject();    
gameMDC->DeleteDC();但是最后显示出来的只是一片黑色区域
是不是代码哪里出问题了
请高手给予解释

Answer 1

gameMDC->CreateCompatibleDC(gameDC); 
===========================
用错了，这个函数一个是创建一个兼容的DC，不是你这样用的。
CWnd *cwnd=FromHandle(hWnd);这个是要被截图的窗口句柄 
CDC *robetDC=this->GetDC();这个是显示图片的窗口DC 
CDC *gameDC=cwnd->GetDC(); 
CDC *gameMDC=new CDC; 
robertDC->CreateCompatibleDC(gameDC); //这句改成这样就行了。
CBitmap *gameMap=new CBitmap; 
gameMap->CreateCompatibleBitmap(gameMDC,100,100); 
gameMDC->SelectObject(gameMap); 
robetDC->BitBlt(50,50,50,50,gameMDC,20,20,SRCCOPY); 
gameMap->DeleteObject();    
gameMDC->DeleteDC(); 

Answer 2

CWnd *cwnd=FromHandle(hWnd);这个是要被截图的窗口句柄 
CDC *robetDC=this->GetDC();这个是显示图片的窗口DC 
CDC *gameDC=cwnd->GetDC(); 
CDC *gameMDC=new CDC; 
gameMDC->CreateCompatibleDC(gameDC); 
CBitmap *gameMap=new CBitmap; 
gameMap->CreateCompatibleBitmap(gameMDC,100,100); 
gameMDC->SelectObject(gameMap); gameMDC->BitBlt(0,0,100,100,gameDC,0,0,SRCCOPY); 
robetDC->BitBlt(50,50,50,50,gameMDC,20,20,SRCCOPY); 
gameMap->DeleteObject();    
gameMDC->DeleteDC(); 

Answer 3

或者：CWnd *cwnd=FromHandle(hWnd);这个是要被截图的窗口句柄 
CDC *robetDC=this->GetDC();这个是显示图片的窗口DC 
CDC *gameDC=cwnd->GetDC(); 
//CDC *gameMDC=new CDC; 
//gameMDC->CreateCompatibleDC(gameDC); 
//CBitmap *gameMap=new CBitmap; 
//gameMap->CreateCompatibleBitmap(gameMDC,100,100); 
//gameMDC->SelectObject(gameMap); robetDC->BitBlt(50,50,50,50,gameDC,20,20,SRCCOPY); 
//gameMap->DeleteObject();    
//gameMDC->DeleteDC();