A Complete Guide to Web Design

274 Chapter 14 – GIF Format

Transparency

Web Design in a Nutshell, eMatter Edition

the channel using any aliased fill or paint tool (just be sure anti-aliasing is turned

off).

Figure 14-5 illustrates how adding a black stroke in the Alpha Channel results in

corresponding transparent areas in the GIF file, allowing the background (in this

case, black) to show through.

The following technique is another alternative for removing fringe and unwanted

pixels around transparent images by carefully adding transparent pixels to the

Alpha Channel.

1. Open a GIF89a file that has transparency information.


2. View the Alpha Channel by selecting WindowsÝ Show Channels, and
   turning on the eye icon in the left column. If the eye icon is activated for both
   channels, the image will show through and the channel will appear as a trans-
   lucent mask.


3. Click on Channel #2 and activate it in order to edit the transparency
   information.


4. In most cases, you’ll only be fine-tuning, so the pencil tool set to a 1- or 2-
   pixel wide brush will do the trick.


5. When you’ve made the desired changes to the channel, simply save the GIF
   file. If you choose to export the file, select “#2” from the “Transparency
   From:” pop-up menu.

Figure 14-5: Editing the alpha channel results in new transparent areas in the

graphic

line drawn in alpha channel

is transparent