anti-aliasing

graphics A technique used on a grey-scale or colour

bitmap display to make diagonal edges appear smoother by

setting pixels near the edge to intermediate colours

according to where the edge crosses them.

The most common example is black characters on a white

background. Without anti-aliasing, diagonal edges appear

jagged, like staircases, which may be noticeable on a low

resolution display. If the display can show intermediate

greys then anti-aliasing can be applied. A pixel will be

black if it is completely within the black area, or white if

it is completely outside the black area, or an intermediate

shade of grey according to the proportions of it which overlap

the black and white areas. The technique works similarly with

other foreground and background colours.

"Aliasing" refers to the fact that many points (which would

differ in the real image) are mapped or "aliased" to the same

pixel (with a single value) in the digital representation.

(1998-03-13)