convert image to line using opencv

how to convert fineline from image to array of cv::point?

I use cvgoodFeaturesToTrack() ,but some point instability.

request a better choice.

see Attach

mayebe ofxCvContourFinder could help?

https://github.com/openframeworks/openFrameworks/blob/master/apps/devApps/ofPolylineTesting/src/testApp.cpp

here a good example how take a polyline from countour finder

thank