WMF limitations

The Windows Metafile image format unfortunately does not provide any unicode support, but stores characters in 8bit ANSI encoding. If you want to display unsupported characters, you can still do so in certain cases by using a Windows font that stores the relevant character in the lower 8bit area. For instance Σ's Unicode encoding is u03A3 and its Windows Symbol encoding is 0x53. So, prior to writing a graph to WMF format, you should relabel any node and edge labels that display a Σ with a capital S and set the label font to Symbol.

Another rather annoying limitation is the fact that WMF stores coordinates as integers which will oftentimes result in rather ugly drawings of e.g. circles and ellipsoids. By writing an upscaled graph (or image in general) in WMF format and then letting a WMF viewer or printer handle the downscaling and/or rounding, this limitation can be somewhat lifted.