旋转图形

旋转公式：

$M(\theta) = \begin{bmatrix} \cos{\theta} & -\sin{\theta} \\ \sin{\theta} & \cos{\theta} \end{bmatrix} = \exp\left(\begin{bmatrix} 0 & -\theta \\ \theta & 0 \end{bmatrix}\right)$

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);