For example a page of printed text having 2000

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Unformatted text preview: takes about 20 seconds to scan a document of size 21 cm x 28 cm. 2. Hand-held scanner. As shown in Figure 9.9, a hand-held scanner has a set of light emitting diodes encased in a small case that can be conveniently held in hand during operation. To scan a document, the scanner is slowly dragged from one end of the document to its other end with its light on. The scanner has to be dragged very steadily and carefully over the document, otherwise the conversion of the document into its equivalent bit map will not be correct. Due to this reason, hand-held scanners are used only in cases where high accuracy is not needed. They are also used when the volume of documents to be scanned is low. They are also much cheaper as compared to flat-bed scanners. Optical Character Recognition (OCR) Device We saw in the description above that image scanners may be used to input a wide variety of documents including pictures, graphics, typed text, or handwritten text. When they are used for inputting text documents (typed c handwritten), they have the following two limitations: 1. Since the input document is stored as an image instead of text, it is not possible to do any word processing of the document (the computer cannot interpret the stored document as letters, number and special characters). 2. The storage required for storing the document as an image is several times more than that required fc storing the same document as a text. For example, a page of printed text having 2000 characters can be stored as 2000 bytes using the ASCII representation. A bit map image representation of the same document will require 10 to 15 times more storage depending on the resolution (granularity) of gri points. The OCR technology is used to overcome these limitations. In this case, the scanner is equipped with a character recognition software (called OCR software) that converts the bit map images of characters to equivalent ASC codes. That is, the scanner first creates the bit map image of the document and then the OCR software translate the array o...
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