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.
Computer printers doing it by varying the density of small dots. Simple algorithms use the same patterns for the same intensity areas but simple patterns should be avoided. There is freedom in the order the pixels are processed.