Convert normal map height map?

Hi

I don’t see an “edit image” on the context menu, I see “Edit Texture” and it opens some view called “PixelHead” which doesn’t seem to have any useful features at all, certainly nothing like image conversion:

Do I have a plugin missing? Or am I just being thick?!

I specifically want to do the conversion programmatically not in a tool - but if it is in the SDK or an open source plugin I can probably rip the code from there.

Thanks