1. Reinhard Klette. 2014. Concise Computer Vision. Springer, London.
2. OpenCV 2015. Canny edge detection tutorial. Retrieved Jan 30, 2019 from docs.opencv.org/3.1.0/da/d22/tutorial_py_canny.html
3. OpenCV 2017. Getting started with contours tutorial. Retrieved Jan 30, 2019 from docs.opencv.org/3.3.1/d4/d73/tutorial_py_contours_begin.html
4. OpenCV 2018. Contour features & moments tutorial. Retrieved Jan 30, 2019 from docs.opencv.org/3.4.2/dd/d49/tutorial_py_contour_features.html
5. OpenCV 2018. Image thresholding tutorial. Retrieved Jan 30, 2019 from docs.opencv.org/4.0.1/d7/d4d/tutorial_py_thresholding.html