Graphics on the Web 39PrinciplesWeb DesignGraphics on the WebWeb Design in a Nutshell, eMatter Editionfile sizes more accurately. Macs shipping with MacOS 8.1 or later may have HFS
Plus-formatted drives.
The resource fork.Macintosh files may contain extra Mac-specific code called the
resource fork,which is used for storing icons, previews, and file type information.
Only the actual data (thedata fork) in the file is readable by other platforms, so
the resource fork should be stripped out when the file is uploaded to a server. The
size of the data fork is the only number you should consider, as it is the actual
number of bytes that will be downloaded by a browser.
Photoshop files.Photoshop usually saves files with an icon and thumbnail views of
the image stored in the resource fork. You can turn these off (saving just the data
fork) by unchecking the Icon and Thumbnail checkboxes under Image Previews
in the PreferencesÝFile Saving dialog box. When you use the GIF89a Export
filter to create GIFs, only the data fork is saved, and its file size will be accurate in
the Get Info window.
Using Snitch.Unfortunately, there is no way, using the Mac Get Info box alone, to
tell how much of the file size is the resource fork and how much is the data fork.
Snitch 2.5 is a shareware utility that works like a beefed-up Get Info window.
When you select Dates & Sizes in the pop-up menu, Snitch shows you the actual
byte sizes of the data and resource forks, as shown in Figure 3-3.
Snitch, written by Mitch Jones, is available for download athttp://www.niftyneato.
com(there is a $20 registration fee if you choose to continue using it). In addition
to Dates & Sizes it contains many useful tools for viewing and editing file type
information.
Figure 3-3: Snitch shows the data fork length and resource fork length of
Macintosh files