如何实现View的按比例缩放功能

[shlife]

各位大哥，如何实现View的按比例缩放功能，很急， 请赐教！

[deyi]

void CView::OnPrepareDC(CDC* pDC, CPrintInfo* pInfo)
{
CView::OnPrepareDC(pDC, pInfo);
pDC->SetMapMode (MM_ANISOTROPIC);
pDC->SetWindowExt (100,100);

int xLogPixPerInch = pDC->GetDeviceCaps(LOGPIXELSX);
int yLogPixPerInch = pDC->GetDeviceCaps(LOGPIXELSY);

pDC->SetViewportExt( (int)(xLogPixPerInch*m_zoomScale),
(int)(yLogPixPerInch*m_zoomScale) );
}


void CView::OnZoomIn()
{
m_zoomScale *= 1.25;
Invalidate();
}