A Complete Guide to Web Design

Minimizing GIF File Sizes 277

GIF

Minimizing GIF File Sizes

Web Design in a Nutshell, eMatter Edition

This may be useful for instances when you want identical transparent areas for a
group of graphics, such as a set of buttons. It is particularly useful if you’ve
somehow edited the Alpha Channel and want to apply that change repeatedly.

1. Open the file that contains the “master” transparency alpha channel (the one
   you want to apply to many graphics). Also open any files you want to copy
   this information into (“copy” files).


2. In the master file, activate Channel #2 in the Channels Palette.


3. Using the pop-up menu from the arrow in the upper right, select “Duplicate
   Channel.”


4. In the Duplicate Channel dialog box, you have the option of naming the
   channel as it will appear in the target files. If you leave the field blank, the
   channel will be named “#2” automatically, which is fine.


5. Choose a destination document from the pull-down menu. The menu gives
   you a list of open files. Once you’ve selected a file, click OK.


6. The “copy” file now has an alpha channel you can use for transparency.
   Export the file to GIF89a (FileÝExportÝGIF89a) and select “#2” (or the
   name you gave the channel) from the “Transparency From:” pop-up menu.
   Click OK.

Minimizing GIF File Sizes

When you are designing and producing graphics for the Web, it is of utmost
importance to keep your file sizes as small as possible. The standard guideline for
estimating download time over a modem is 1 second per kilobyte. Of course,
actual download times will vary widely, but it at least gives you a ballpark number
to use for comparisons.

There are a few simple strategies you can follow to minimize the size of your GIF
files.

Design Strategies

You can help keep file size under control by the design decisions you make. After
a while, designing for the Web becomes second nature.

Figure 14-9: Type is restored to Transparency Indexed Color (which has been set to
white)