如何在指定矩形中旋转显示文字

///////////////////////////////////////////////////////
//说明：
//  在矩形框中旋转方式显示文字，jingzhou xu
//参数：    
//  pDC:      DC指针
//  str:      显示文字
//  rect:      显示范围
//  angle:      旋转角度
//   nOptions:   ExtTextOut()中相应设置<ETO_CLIPPED 和 ETO_OPAQUE>
///////////////////////////////////////////////////////
void DrawRotatedText(CDC* pDC, const CString str, CRect rect,
                     double angle, UINT nOptions)
{
   //按比例转换角度值
   double pi = 3.141592654;
   double radian = pi * 2 / 360 * angle;

   //获取显示文字中心点
   CSize TextSize = pDC->GetTextExtent(str);
   CPoint center;
   center.x = TextSize.cx / 2;
   center.y = TextSize.cy / 2;

   //计算显示文字新的中心点
   CPoint rcenter;
   rcenter.x = long(cos(radian) * center.x - sin(radian) * center.y);
   rcenter.y = long(sin(radian) * center.x + cos(radian) * center.y);

   //绘制文字
   pDC->SetTextAlign(TA_BASELINE);
   pDC->SetBkMode(TRANSPARENT);
   pDC->ExtTextOut(rect.left + rect.Width() / 2 - rcenter.x,
                   rect.top + rect.Height() / 2 + rcenter.y,
                   nOptions, rect, str, NULL);
}

用法：
   DrawRotatedText (pDC,”VC知识库”,CRect(100,100,300,300),15, ETO_CLIPPED);