Is there any idea for finding the blue line with any kind of shape? (for example the alphabet)
Thanks for the idea! I am still thinking about this
This approach can be followed:
or use the polyskel component from ladybugtools.
What you are after is called Medial Axis. There are several topics about this on the forum with various solutions depending on the complexity of the shape.
For letters, the accuracy of the result will likely depend on the font.
Thank you guys! so much appreciated it! I will check and find out how to do a better one and share the result again.