旋转公式:
XFORM xForm;
double pi = 3.1415926;
xForm.eM11 = (FLOAT)cos(pi/6);
xForm.eM12 = (FLOAT)sin(pi/6);
xForm.eM21 = (FLOAT)-sin(pi/6);
xForm.eM22 = (FLOAT)cos(pi/6);
xForm.eDx = (FLOAT)0.0;
xForm.eDY = (FLOAT)0.0;
SetGraphicsMode(pDC->m_hDC,GM_ADVANCED);
pDC->SetMapMode(MM_LOENGLISH);
SetWorldTransform(pDC->m_hDC,&xForm);
RECT rect;
GetClientRect((LPRECT)&rect);
pDC->DPtoLP((LPPOINT)&rect,2);
pDC->Ellipse(rect.right/4,rect.bottom/4,3*rect.right/4,3*rect.bottom/4);