GIF File Sizes on Macs. Copyright 1996 BoxTop Software, Inc. All rights Reserved.
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File sizes are very important for World Wide Web graphics. Smaller files mean shorter transmission times and more viewers that stick around to see your page. With this in mind we've take great pains to develop superior technology for PhotoGIF¬ that allow you to make the smallest, best looking GIF files possible with it.
This includes the adaptive and fixed palette color reduction, which uses a new variable intensity, selective dithering technique that minimizes entropy and produces more compressible image data; a palette usage optimization feature that removes redundant colors from the image and reorganizes color usage to specifically improve compression; and the most efficient LZW compression there is.
Still, we sometimes get asked, 'Why are PhotoGIF¬ files so much bigger?' The answer is the GIF files aren't really bigger. Almost always, they are smaller.
There are several things that can make them appear bigger. The most common explanation of why the files look bigger in your Mac's 'get info' box is that it normally shows the combined size of the Mac files data fork (the actual GIF file) and the Mac files resource fork where Photoshop stores custom icons, previews and other image resources such as the last window position.
The second thing is the way the Mac allocates disk space for files in fixed size blocks. These blocks vary in size according to the size of your hard drive (or partitions on it) and can get quite big in comparison to the actual size of the file. A 500 byte GIF file could be stored in a 32K chunk of disk space, and a quick glance at the 'get info' box can be misleading if you only look at the first number which shows the disk space allocated for the file and not the number of bytes used in the file.
Now, the thing you need to be aware of is the difference in the Mac file system and the file systems of the rest of the computers in the world that wouldn't know what a resource fork was if it bit them on the nose. When you send your Mac files as binary data to your server only the 'data fork' is transferred. (Unless you specifically use an encoding method such as binhex or MacBinary to preserve the resource fork of the Mac file, which you DO NOT want to do since it would render your web page graphics as broken image icons.)
Whatever was in the resource fork is still sitting on your desktop, and only the data fork, the actual GIF file, is on your server. Even if you have a Macintosh web server what is in the resource fork of the file is never sent in response to an http request, so either way the extra information stored in the resource fork of the file doesn't make a bit of difference as far as bandwidth is concerned.
So it doesn't hurt a bit to keep those custom icons and image previews that make life so much easier around. If you really want to you can tell Photoshop not to make them in it's preferences settings and save file dialog, but it's really not necessary.
PhotoGIF¬ 2.1 is Copyright 1996 BoxTop Software, Inc. All rights reserved. PhotoGIF¬ is a Trade Mark of BoxTop Software, Inc.
