Bresenham algorithm

In your implementation you need to handle all slopes!

First, reorder endpoints so that x1, <= x2

Then consider 4 cases:

y2,-y1 >= 0, x2,-x1 >= y2,-y1 positive slope <= 1

y2,-y1 >= 0, x2,-x1 < y2,-y1 positive slope > 1

y2,-y1 < 0, x2,-x1 >= y1,-y2 negative slope >= -1

y2,-y1 < 0, x2,-x1 < y1,-y2 negative slope < -1

In each case, make appropriate substitutions in

the algorithm.

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