If odd, the point is contained. Start and recurse.
Clipping is similar to filling, except, it is for a line with arbitrary orientation.
Border crossings have to be determined as before. Halftone algorithms and dithering Simulate, or give the appearance of more colours on the screen than physically possible to show. Demonstration can be made with black and white pixels only and the achievement of grey scale images. Either the resolution or the contrast of the image must suffer. Newspapers do it by varying the size of the black dots.