Hi, this is a great work that I like so much! Thanks for your work.
The problem is I have a bright image(a photo captured by camera and I adjust it to a very bright version, see attachment) input into the Lindraw algorithm, but get blank result.
I have tried original linedraw.py, it works fine. I attach the image file and the output of linedraw.py, please take a look.
Tuning the parameters makes no help.
Original image:

linedraw.py output:
