Animated GIF

graphics, file format (GIF89a) A variant of the GIF

image format, often used on World-Wide Web pages to

provide moving icons and banners.

The GIF89a format supports multiple "frames" that give the

impression of motion when displayed in sequence, much like a

flip book. The animation may repeat continuously or play

once.

Animated GIFs aren't supported by earlier web browsers,

however the first frame of the image is still shown.

There are many utilities to create animated GIFs from a

sequence of individual GIF files. There are also utilities

that will produce animated GIFs automatically from a piece of

text or a single image.

One problem with this format is the size of the files

produced, as they are by definition a sequence of individual

images. Apart from minimising the number of frames, the best

way to decrease file size is to assist the LZW compression

by using blocks of solid colour, avoid dithering, and use

fewer colours. If areas of an image don't change from one

frame to another, they don't need to be redrawn so make the

area a transparent block in the second frame.

(1999-08-01)