Computer icons are an integral part of any modern GUI. Icons are small pictograms of standardized resolutions that depict objects, actions, and symbols. In window-based systems, icons are used as a quicker, more intuitive way to communicate with the user. Icons depicting standard elements of a user interface are better visible than text, can be recognized faster, and are easier for new computer users.
Originally introduced in 1970 by the Xerox Research Center and widely popularized by the Mac OS and Microsoft Windows platforms, icons make computer novices feel more comfortable with computer systems, learn quicker and work more efficiently. Icons can be used to replace or supplement text commands. Commonly used in menus, toolbars, on buttons and in new ribbon-style user interfaces, icons have come a long way from the original concept.
There are multiple graphic formats for storing icons. The Windows systems store Windows icons in the platform-specific ICO format. Apple Macintosh systems use Mac icons in their specific formats, while Unix-based systems use PNG icons for most applications. As such, icon editing software is generally available for the Windows and Apple platforms, while Unix users can design PNG icons with any graphic editor.
As a rule of thumb, icons are square pictures that come in a variety of standard sizes and color resolutions. Most platforms use icon sizes of 16×16 to 128×128 pixels, while some systems readily accept icon images as large as 512×512 pixels. The high-resolution 512×512 pixel icons were first used in Mac OS Leopard.
Pixel dimensions of all icons are operating system dependent. For example, Windows icons are specified as pictures in 16 and 256-color gammas as well as True Color images with alpha channel. Windows icons are supplied in standard sizes of 16×16, 32×32, and 48×48 pixels. Windows Vista defines new standards for Windows icons, including icons in resolutions of up to 256×256 pixels in True Color only. Optionally, images of 128×128 and 512×512 pixels are supported. Interestingly, the high-resolution Windows Vista icons are stored in compressed PNG format instead of Windows ICO used in older versions of Windows and for lower resolution images. Other platforms such as Windows Mobile can employ standard icons of other resolutions, such as 24×24 pixels.
Many independent designers are offering custom icons. Aha-Soft offers a variety of Windows icons, Mac icons, and PNG icons in all sizes and resolutions common to those platforms. The company sells royalty-free icons individually and in matching sets incorporating icons drawn a common style or theme.