Appendix I: About Gif Animation - Ulead GIF ANIMATOR 4.0 User Manual

Appendix I: About GIF animation

GIF is an acronym for Graphics Interchange Format, an image file format created by
CompuServe for conveniently storing and displaying image libraries online. Because of its
completely 'lossless' compression and relatively small file size, the GIF file format has become
one of the most widely used image file formats on the Internet today. GIF has undergone two
major revisions since its inception in 1987, the most recent being the GIF89a specification.
GIF uses the Lempel-Ziv-Welch (LZW) compression method to store and reduce single or
multiple images within the file by up to 40% of their original size. These images can contain up
to 256 colors, and they do lose any of their original quality when being compressed down to
more web-friendly sizes as long as they originally contained 256 colors or less. Even though
GIF is a lossless format, images that are imported from other file formats and converted to
GIF may lose some of their quality in the transition from True Color to 256-color. This is
often the case when working with outside image editors to create the individual frames of the
animation. GIF files also possess transparency attributes so that one color in the image is not
displayed. This allows users to create clear backdrops for their images, letting the background
colors of a web page show through. The file format also supports image interlacing, allowing
users to watch the image "fade-in" as it downloads, although for multiple image GIFs (anima-
tions), interlacing is disabled beyond the first image layer.
If multiple images are stored within a GIF file, they can be viewed sequentially, much like a
slide show or an animated movie. The way they appear is defined by control extensions built
into the file. With an appropriate tool, such as Ulead GIF Animator, you can set these controls
yourself and bring your web site to life with exciting cartoons, banner ads, glowing bullets,
and other animations.
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