如何从一个CBitmap或是资源位图中截取一部分到另一个CBitmp中

void CSkinAnalyseDoc::GetRectBmp(CBitmap *pDesBmp, CBitmap *pSrcBmp, CRect rc, CView *pParent)

{

//     CClientDC MemDC(pParent);

//     CDC showDC;

//     showDC.CreateCompatibleDC(&MemDC);

//

//     CBitmap *pOldBmp1 = MemDC.SelectObject(pSrcBmp);

//     CBitmap *pOldBmp2 = showDC.SelectObject(pDesBmp);

//     showDC.BitBlt(0, 0, rc.Width(), rc.Height(),\

//                            &MemDC, rc.left, rc.top, SRCCOPY);

//

//     MemDC.SelectObject(pOldBmp1);

//     showDC.SelectObject(pOldBmp2);

//     showDC.DeleteDC();