This pic looks like a drainage flow diagram.If so, you may simply just need to transform a pic into a 3D topo based on the grayscale, and do a flow simulation in kangaroo, of which both tutorials would be easily found on youtube.
Thank you. Could you tell me how to search on youtube? What are the keywords? I tried, but I couldn’t find them.
For instance:
Also, there are multiple ways to approach similar result
1920 x 1920 = 3,686,400 points! But curves? That’s a different story. Image Sampler gives you color values or brightness, which you could filter to get only the points that meet your criteria but still, there are many curves in that image.
thank you
Thank you for your reply. I want to construct a light blue curve by connecting points, the kind in the pattern
How to draw the curve in the picture with grasshoppers?
There are hundreds (thousands?) of curves in that image. I don’t think Image Sampler will help.
I have this tool
But the image is low quality, it is better if you make yourself the drainage, you’ll have better results.
Thank you very much! Next, I’ll process the picture first.
Excuse me, why do I output null values after importing pictures?
Looking forward to your plug-in release.
Surely because the default threshold is not good for your image.
20230226_image thinner.gh (7.4 KB)
Play with the slider, it must work better.
Because I am not familiar with C#, I bother you again. Thank you very much for your answer. Thank you!
So the solution is a black box that you can’t understand or modify… 
I sincerely hope you have no plans to become an engineer.
There is still a long way to go, so I have no plan for the time being. 