HTML and CSS Reference
also insert a transparent image inline with conventional text to act as a
special character glyph within conventional text.
The downside to transparency is that the GIF image will look lousy if you
don't remove its border when it is included in a hyperlink anchor ( <a> )
tag or is otherwise specially framed. And content flow happens around
the image's rectangular dimensions, not adjacent to its apparent shape.
That can lead to unnecessarily isolated images or odd-looking sections
in your web pages.
The third unique trick available with GIF89a-formatted images is the
ability to do simple frame-by-frame animation. Using special GIF-anima-
tion software utilities, you may prepare a single GIF89a file that contains
a series of GIF images. The browser displays each image in the file, one
after the other, something like the page-flipping animation booklets we
had and perhaps drew as kids. Special control segments between each
image in the GIF file let you set the number of times the browser runs
through the complete sequence (looping), how long to pause between
each image, whether the image space gets wiped to background before
the browser displays the next image, and so on. By combining these
control features with those normally available for GIF images, including
individual color tables, transparency, and interlacing, you can create
some very appealing and elaborate animations. [*]
[*] Songline Studios has published an entire book dedicated to GIF animation: GIF Animation Studio ,
by Richard Koman.
Simple GIF animation is powerful for one other important reason: you
don't need to specially program your HTML documents to achieve anim-
ation. But there is one major downside that limits their use for anything
other than small, icon-size, or thin bands of space in the browser win-
dow: GIF animation files get large fast, even if you are careful not to
repeat static portions of the image in successive animation cells. And if
you have several animations in one document, download delays mayand
usually willannoy the user. If any feature deserves close scrutiny for ex-
cess, it's GIF animation.
Any and all GIF tricksinterlacing, transparency, and animationdon't just
happen; you need special software to prepare the GIF file. Many image