CScrollView怎么刷新背景图象?

我建立了一个CScrollView,然后为View加了一幅背景画IDR_BKG,但是每次往下拉滚动条都会出现图象变花\重影,请问该怎么解决?
void CGraphView::OnInitialUpdate() 
{
CScrollView::OnInitialUpdate();

// TODO: Add your specialized code here and/or call the base class
SetScrollSizes(MM_TEXT,CSize(800,600));
}
BOOL CGraphView::OnEraseBkgnd(CDC* pDC) 
{
// TODO: Add your message handler code here and/or call default
OnPrepareDC(pDC);
CBitmap bmp;
bmp.LoadBitmap(IDR_BKG);
CDC dcComp;
dcComp.CreateCompatibleDC(pDC);
dcComp.SelectObject(&bmp);
//BITMAP bmps;
//bmp.GetBitmap(&bmps);
CRect rect;
GetClientRect(&rect);
pDC->BitBlt(0,0,rect.Width(),rect.Height(),&dcComp,0,0,SRCCOPY);
return 1;
//return CScrollView::OnEraseBkgnd(pDC);
}