在位图上画的图像老是闪，求大虾帮忙看看

void CColligateDlg::OnDrawWheel(CDC &pDC)
{ CDC MemDC;
COLORREF WhiteColor = RGB(0,0,0);
 
CBrush WhiteBrush(WhiteColor);
CPen Whitepen(PS_SOLID,1,RGB(255,0,0));
    char tmp[10];
    MemDC.CreateCompatibleDC(&pDC); pDC.SelectObject(&WhiteBrush);
pDC.SelectObject(&Whitepen);
//--------------------------------------------------舵角角度指针绘制---------------------------------------------
   double a = 90 - counter/2;
   a *= PI / 720.0;
   double b = PI/2 - a;
   POINT points4[4] =
   {
   {391-5*cos(4*b+PI*3/2),599-5*sin(4*b+PI*3/2)},//左                // 688 , 500 
   {391+80*cos(4*a),599-80*sin(4*a)},            //上
   {391+5*cos(4*b+PI*3/2),599+5*sin(4*b+PI*3/2)},//右    
   {391-5*cos(4*b+PI*3/2),599-5*sin(4*b+PI*3/2)}//左
};   POINT points5[4] = 
   {
   {391-5*cos(4*b+PI*3/2),599-5*sin(4*b+PI*3/2)},
   {391 -10*cos(4*a),599+10*sin(4*a)},
   {391+5*cos(4*b+PI*3/2),599+5*sin(4*b+PI*3/2)},
   {391-5*cos(4*b+PI*3/2),599-5*sin(4*b+PI*3/2)}
   }; pDC.Polygon(points4,4);
pDC.Polygon(points5,4); //-------------------------------------舵角输出数据值-----------------------------------------------------
CFont myfont;
myfont.CreateFont(30,
0,
0,
0,
FW_BOLD,
FALSE,
FALSE,
0,
ANSI_CHARSET,
OUT_DEFAULT_PRECIS,
CLIP_DEFAULT_PRECIS,
PROOF_QUALITY,
DEFAULT_PITCH | FF_SWISS,
"Arial");
CFont *oldFont = pDC.SelectObject(&myfont);
COLORREF Pcolor = RGB(196,7,3);
COLORREF oldcolor = pDC.SetTextColor(Pcolor);
pDC.SetBkMode(TRANSPARENT);
sprintf(tmp,"%10.0f%",fabs(counter/1.8));
pDC.TextOut(325,615,tmp);
//------------------------------------------水深---------------------------------------------------------------
COLORREF GreenColor = RGB(228,239,243);
CBrush Green(GreenColor);

CPen GreenPen;
GreenPen.CreatePen(PS_SOLID,3,GreenColor);

pDC.SetTextColor(GreenColor);              
pDC.SelectObject(GreenPen);
pDC.SelectObject(&Green);
    pDC.RoundRect(CRect(823,342,938,452 + counter),CPoint(5,5)); pDC.BitBlt(0,0,1024,768,&MemDC,0,0,SRCCOPY);

}