I need to use cv::FindContours() in a program and I have to know the algorithm behind that.
What algorithm does openCV use to find contours?
How does it work?
If you read the documentation it is mentioned this function implements the algorithm of:
Suzuki, S. and Abe, K., Topological Structural Analysis of Digitized Binary Images by Border Following. CVGIP 30 1, pp 32-46 (1985)
OpenCV is open source if you want to see how this is implemented just need to read the code: https://github.com/opencv/opencv/blob/master/modules/imgproc/src/contours.cpp#L1655
The paper is available here.