Adding Icons to Applications
Mac OS X uses icons — little descriptive pictures — in many places to represent programs and their documents. Mac OS X also allows applications to change their icons while the applications are running. For example, the Mail program uses the icon containing an envelope to represent the application in the Dock and Finder. When Mail is active and you have unread mail messages, the Mail program adds an icon badge to its icon in the Dock to display how many messages are unread. As we’ve seen already, folders and documents also have icons.
Viewing Icons with the icns Browser Application
Application icons are typically stored
in a file with a
extension. Each such file contains
several images, of various sizes and bit depths, that are used by the
Finder and other applications. A
.icns file can
also contain an icon mask that is used for transparency. Because
bitmap images do not scale well, the
format stores only icons that are 12 x 16, 16 x
16, 32 x 32, 48 x 48, or 128 x 128
pixels. You can simultaneously view all of the images for a given
file with the icns Browser application, located in the
The Mac OS X Mail application icons are stored in the file
This file doesn’t normally appear in the Finder
because the Finder hides system details from users. However, you can
see the contents of the
file by first choosing
Finder’s Go → Go to Folder command ...
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