A renderer for a subset of PostScript, creates anti-aliased grayscale images from glyphs that were produced with pbm2glyph.

Without anti-aliasing, there are only black and white pixels in the output. The result looks like this. A closer look shows that there are pixel stairs.

With anti-aliasing, pixels will be gray if they're on the border of the glyph. This lets the output appear much smoother.