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A_bit_about_file_sizes
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A Bit About File Sizes ⌐ BoxTop Software. All rights Reserved.
BoxTop Software
P.O. Box 2347
Starkville, MS 39760
1 (601) 324-7352
boxtop@aris.com
http://www.aris.com/boxtop/PhotoGIF
ftp://aris.com/boxtop
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 care to incorporate
one of the best LZW compressors around into PhotoGIF. We haven't found a
Macintosh application yet capable of saving GIF89a files that beats
PhotoGIF's compression. It beats GIF89a Export, it beats Debabelizer, and
it beats Graphic Converter.
Still, we get asked all the time, 'Why are PhotoGIF files so much bigger?'
The answer is the GIF files aren't. 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 for 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, but it's really
not necessary.