When looking at the circle representation on a graphics device ,  which distance between the rows of pixles is different from the distance between the columns, it is obvious that the circle on the screen looks like an ellipse.

     The construction of a centred ellipse can be done by the Bresenham's algorithm, similarly as at the circle,
while we have to compute the values as a quadrant  of a circle.

Algorithm is used from John Kennedy paper : http://homepage.smc.edu/kennedy_john/


Ellipse select corner point (right mouse button) for new ellipse. Author Marián Rojko

Source code