Article #1
The terms wallpaper and desktop picture refer to an image used as a background on a computer screen, usually for the desktop of a graphical user interface. 'Wallpaper' is the term used in Microsoft Windows, while the Mac OS calls it a 'desktop picture' (prior to Mac OS X, the term desktop pattern was used to refer to a small pattern that was repeated to fill the screen).
Images used as computer wallpaper are usually raster graphics with the same size as the display resolution (for example 1024×768 pixels, or 1280×1024 pixels) in order to fill the whole background. Many screen resolutions are proportional, so an image scaled to fit in a different-sized screen will often be the correct shape, albeit that scaling may impact quality. PNG and JPEG format are common. Users with widescreen (16:9 or 16:10) monitors have different aspect ratio requirements for wallpaper, although images designed for standard (4:3) monitors can often be scaled or cropped to the correct shape without loss of quality. Wallpapers are sometimes available in double-width versions (e.g. 2560×1024) for displaying on multi-monitor computers, where the image appears to fill two monitors. Some display systems allow unconventionally-proportioned images (1:1, 2:1, or even 1:3) to be scaled without change of proportion, to fit the screen, whether it be 16:9 or 4:5. The image would be sized just large enough that one pair of edges touch the edges of the screen, but not all four, as this would unduly distort the image. Smaller images can usually either be centered or tiled (repeated) to fill large areas, and depending on how skilfully the wallpaper was created, the tiling effect can look reasonably good. However, if the join is too obvious, or the image repeats too many times, it can appear to be very redundant. With the increase in color screen mobile phones, wallpapers are starting to appear scaled to their lower resolution. These are often sold at a high profit to telephone users, although some phones have software which allows images to be uploaded from a computer. Mobile telephones with cameras can often use images from the camera, or from a received image, as the wallpaper. Most display systems are capable of specifying a single-colour to use as the background in place of a wallpaper, and some (such as KDE) allow colour-gradients to be specified. Microsoft Windows 3.x and 9x systems allow using editable repeating two-color 8x8 tiles for background. Some desktop systems, like Mac OS version 8.6 or later, or KDE version 3.4 or later, support vector wallpapers in PICT or SVG format, respectively. This has the advantage that a single file may be used for screens of any size, or stretched across several screens, without loss of quality.
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