Scaling bitmaps produces `jaggies'; scaling an outline preserves sharpness. However, traditionally type designers designed each size of a font separately, smaller sizes tending to be more squat than larger sizes. Designing a font for use at any size inevitably involves compromises. Knuth's Metafont program uses a far more complex font description, which produces different shapes at different sizes. As a consequence, font generation by Metafont is a rather slow process; it would probably be too slow for the on-the-fly font generation done inside PostScript printers.