scanner (computing)

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In computing, a device that can produce a digital image file of a document for input and storage in a computer. It uses technology similar to that of a photocopier. Small scanners can be passed over the document surface by hand; larger versions have a flat bed, like that of a photocopier, on which the input document is placed and scanned.

Scanners are widely used to input graphics for use in desktop publishing. If text is input with a scanner, the image captured is seen by the computer as a single digital picture rather than as separate characters. Consequently, the text cannot be processed by, for example, a word processor unless suitable optical character-recognition software is available to convert the image to its constituent characters. Scanners vary in their resolution, typical hand-held scanners ranging from 75 to 300 dpi (dots per inch).

Scanners also exist to scan photographic film and transparencies. These devices are used by people who take pictures with conventional cameras but then want to make a high-quality digital copy of the picture in order to manipulate the image in some way or print the image on a computer printer. Film scanners are now capable of scanning at resolutions of 4,000 dpi, and with 42-bit colour depth.

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