What Is Icon?
Computer icons are an integral part of any graphical user interface. Icons are small pictograms of standardized sizes that visually represent objects, actions, symbols, and other concepts. In graphical user interfaces, icons are used as a faster, more intuitive way to communicate with the user. Icons representing standard elements of a user interface are more visually appealing than text, can be recognized faster, and are certainly easier on the eyes.
Originally introduced in 1970 by the Xerox Research Center and widely popularized by the Apple Macintosh and Microsoft Windows platforms, icons make computer novices feel more comfortable with computer systems, learn faster and interact more efficiently. Icons can be used to replace or supplement text commands. Widely 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 several graphic formats for storing icons. Microsoft Windows systems use Windows icons in the platform-specific ICO format. Apple Macintosh computers 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 Mac OS platforms, while Unix users can create their icons with just about any graphic editor.
As a rule of thumb, icons are square images that come in a number of standard sizes and color resolutions. Most systems support icon sizes of 16x16 to 128x128 pixels, while some platforms readily accept icon images as large as 512x512 pixels. The ultra-high definition 512x512 pixel icons were first employed in Mac OS Leopard.
Pixel dimensions of all icons are operating system dependent. For example, Windows icons are specified as images in 16 and 256-color gammas as well as True Color images with alpha channel. Windows icons come in standard sizes of 16x16, 32x32, and 48x48 pixels. Windows Vista defines new standards for Windows icons, including icons in resolutions of up to 256x256 pixels in True Color only. Optionally, images of 128x128 and 512x512 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 sizes, e.g. 24x24 pixels.
Many independent vendors are offering custom icons. Aha-Soft http://www.777icons.com/ offers a variety of Windows icons, Mac icons, and PNG icons in all sizes and resolutions standard to those platforms. The company sells royalty-free icons individually and in matching sets incorporating icons drawn a common style or theme.