Python; Numpy, MatplotLib, Pyplot, PIL, Pillow, ... tutorials

http://www.labri.fr/perso/nrougier/teaching/numpy/numpy.html

http://www.labri.fr/perso/nrougier/teaching/numpy.100/index.html

https://www.labri.fr/perso/nrougier/teaching/matplotlib/

https://matplotlib.org/users/pyplot_tutorial.html

http://prancer.physics.louisville.edu/astrowiki/index.php/Image_processing_with_Python_and_SciPy

https://www.safaribooksonline.com/library/view/programming-computer-vision/9781449341916/ch01.html

http://forum.imagej.net/t/beginner-question-threshold-of-low-contrast-objects/1206/2

https://mathematica.stackexchange.com/questions/124060/object-detection-in-a-low-contrast-image