>... if you are limited to pure black/white only...

Yes think this goes to the heart of the problem. In effect you aren't allowed shades of grey. [In my opinion this make the patent system out of date to the point of being completely moronic... but it is what it is, I suppose.]

But this lack of shades of grey pixels goes deeper... Because if your CAD system need to create a very fine line, if it is anti-aliasing then it will of course generate grey pixels and if they are pale grey they would simply disappear. Whereas the patent offices sound like they want dotted (i.e. broken) lines rather than grey lines.

Nightmare.