c#: Are there any libraries to analysis Graph?

Question

I need to know if there are libraries that can analysis or read data from graph "saved as image"

Example:

I need to read point for everyday from graph that saved as image and convert it to data to use it

and i can generate data as following

day 1-->20

day 2-->25

day 3-->38

day 4-->23

............ etc

c#