I would like to define specific points or areas of characters:
- uppermost / lowermost point
- horizontal line (like in the m and p in the image where the top horizontals are not the uppermost parts of the letter)
- vertices (like uppermost parts of the m)
- closed counters
I will use this information to draw lines or fill in colors to show typographic characteristics:


Which packages do I need and how can I define these points?