双缓冲gdi+旋转图像固定角度

HDC hdc= m_PaintManager.GetPaintDC();HDC hMemDC = ::CreateCompatibleDC(hdc);HBITMAP hMemBitmap = ::CreateCompatibleBitmap(hdc, 347, 217);::SelectObject(hMemDC, hMemBitmap);RECT myRect;myRect.left = 0;myRect.top = 0;myRect.right = 347;myRect.bottom = 217;::FillRect(hMemDC, &myRect, m_hBrushBackground);RECT SrcRect = m_pCompassVer->GetPos();Matrix matric(1,0,0,1,myRect.left, myRect.top);Graphics      gp(hMemDC);gp.DrawImage(m_pImageCompass,myRect.left, myRect.top, m_pImageCompass->GetWidth(), m_pImageCompass->GetHeight());matric.RotateAt(-180 + angle, m_PtCenter);gp.SetTransform(&matric);gp.DrawImage(m_pImageFinger, 160,170,114,30);gp.ReleaseHDC(m_PaintManager.GetPaintDC());angle +=2;::BitBlt(hdc,SrcRect.left, SrcRect.top, 347, 217, hMemDC, 0, 0, SRCCOPY);::DeleteObject(hMemBitmap);::DeleteDC(hMemDC);