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GIFWeb Design in a Nutshell, eMatter EditionChapter 14GIFCHAPTER 14
GIF Format
GIF (Graphic Interchange Format) was the first graphic file type to be displayed by
early web browsers, and it remains the most popular and versatile format for
distributing color images on the Web to this day. Any image type can be saved as
a GIF, but they excel at condensing graphical images with areas of flat color.
GIFs are completely platform independent, meaning a GIF created on any plat-
form can be viewed and edited on any other platform. They were originally
developed by CompuServe to distribute images over their network to a variety of
platforms (this is why you sometimes see GIFs referred to as “CompuServe GIF”).
It is also the only graphic file format that is universally supported by all graphical
browsers, regardless of version. If you want to be absolutely sure everyone will
see your graphic, make it a GIF.
GIF87a versus GIF89a
There are technically two types of GIF file: the GIF87a and the newer, improved
GIF89a. Both are fully supported on most browsers, and both use.gifas their file
name suffix.
GIF87a is the original format for indexed color images. It uses LZW compression
and has the option of being interlaced.
GIF89a is the same, but also includes transparency and animation capabilities. If
you want to add these features to your graphic, you’ll need to create the graphic
with a tool that supports the GIF89a format. These features have become so
popular with web developers that this format has become thede factostandard on
the Web today. Detailed descriptions of each feature appear in the following
sections of this chapter.