Creating Transparent GIF Files With GIMP

Transparent GIF (Graphics Interchange Format) files are similar to other GIF files but have the property that one color is "transparent" meaning that the background color will show through. This is useful when you wish to create round or irregularly shaped "buttons" on a web page. The image displayed on the web page is actually rectangular, but having a transparent background only the round portion of the image is seen. The background of the web page is seen where the transparent color of the GIF file appears.  A GIF file uses an 8 bit color table, providing a pallet of 256 colors. Any 8 bit value can be selected as a transparent color.

A very good use of transparent GIF files is for the display of e-mail addresses. Displaying e-mail in an image prevents automated tools to examine web pages and "harvest" emails in order to send spam. Here is an example of a table with two gif files inserted. One file was created having a transparent background and the other does not.

Transparent:  Transparent gif non-transparent:  Non-transparent gif

Stepts to create the signature as a GIF file with transparent background:
  1. Select "File -> New".   Create a reasonably good size window, say 400 by 400 pixels. The size doesn't mater as long as it is large enough for the string created.
  2. Put cursor somewhere in the new window. Don't "click" in the window, just move cursor in it.
  3. Use "CTRL-L" to bring up the layers window.
  4. Click the plus sign in the lower left corner of the layers window to create a new layer. Make sure "transparency" is checked in the "create new layer" window.
  5. In the "layers" window click the "background" layer and drag it to the trash can in the lower right corner. This should leave you wiht only the new (transparent) layer.
  6. In the window you first created click Tools -> Text.
  7. Click in the window and a text creation box should appear. Enter the desired e-mail address and click "Close".
  8. Select "Image -> Autocrop".
  9. Select "File -> Save As".
  10. Enter desired name with the ".gif" extension.
  11. Check "Merge visible layers".
  12. Check "Convert to indexed".
  13. Click "Export" and "OK".