Problem
1. Modify a line-drawing algorithm so that the intensity of the output line is set according to its slope. That is, by adjusting pixel intensities according to the value of the slope, all lines are displayed with the same intensity per unit length.
2. Define and implement a function for controlling the line type tsolid, dashed, dotted) of displayed ellipses.
3. Define and implement a function for setting the width of displayed ellipses.