You can try something like this:
private void m_map_ExtentChanged(object sender, ExtentEventArgs e)
{
Envelope pNewEnv = e.NewExtent;
double pWidthScreen = m_map.Width * f_glob._pixel_size;
double pWidthMap = m_map.Extent.Width;
double pScale = pWidthMap / pWidthScreen;
foreach (Graphic pGraphic in pGraphicLayer)
{
PictureMarkerSymbol pSymbol = (PictureMarkerSymbol)pGraphic.Symbol;
pSymbol.Width = your number/pScale;
pSymbol.Height = your number/pScale;
}
}
2 questions:
1. What is f_glob supposed to be?
2. What is "your number"?