Digital scanner

Digital scanner | Scanner: This is a device which scans a document or scene and senses the colour and intensity of each of a number of finite positions called pixels.

Use Optical Character Recognition (OCR) - Scanning pages of text  - this may then be converted into ordinary text. Capturing images for use as drawing templates or for tracing programs Capturing images for use in desktop publishing Helping visualise layouts when your photos will be processed traditionally Making signs scanning 3-Dimensional objects Converting hardcopy images or documents into a Fax format for PC Fax boards Creating new fonts by tracing scanned characters Invitations and announcements Reading solutions for the blind or visually impaired Technical reports and presentations

Features Scanning an image is like taking a picture with a camera. Instead of natural light, the scanner light bar and lens expose the image on the scanner glass. Instead of file, the scanning software and computer electronically store the data of the image. Just like a camera scanning software lets you select brightness and contrast. However , the scanner also allows you to specify the final size of the picture (enlarged or reduced) , the type of picture you wish to save (eg. Black & White, Colour), the eventual destination device (Screen, Printer) so that the eventual image may be different from the original. The data for each pixel is stored as a number for future retrieval and display on a VDU or plotter, or for conversion to a standard picture file format, such as a Bitmap. (Pictures used in this help file). May be a flat-bed device where picture or document to be scanned is positioned flat on the scanner, or a hand-held device, where the scanner is moved over the document or picture to be scanned. During the scanning process; the scanner applies a light source to your image. The light is reflected back from the image into the scanner optics where the varying levels of light are interpreted. Your image is then reconstructed digitally and displayed on your screen.

Images fall into three categories;

• drawings, or line art, include only black and white areas with no intermediate shades of grey. For example, architectural plans, mechanical drawings, pen and ink cartoons, pencil drawings.
• halftones, an image type that simulates grey or colour by varying the number of dots per inch (or centimetre)
• photos, continuous shades from white to black, with all the greys in between, or continuous colour tones and hues.

256 colour and 16 colour.

TWAIN standard

a standard interface for image processing on the computer
The common platform for Macintosh and Windows applications

Hannover, 12 March 1992.

Five market leaders presented a common platform for image processing at the CeBIT in Hannover. The Twain applications interface allows image sources such as scanners, digital cameras and graphic files to be accessed directly from within desktop publishing programs. Twain is available to hardware manufacturers and software developers as a toolkit. The first version ran under Macintosh system 6.05 and higher, and also under Windows 3.0 and higher.

Any scanner you get should come with a Twain driver, which will typically function as a standalone program for scanning, as well as scan images directly into most Windows programs. If an application supports Twain (which has retroactively come to stand for technology without an interesting name), it usually lets you call up the Twain driver by entering a scan (or acquire) command.

Twain drivers may be mini image-editing applications, so users can make whatever tweaks they need to an image without ever having to learn a second software package.

Almost all scanners today also come with scanner-related applications for optical character recognition (OCR), image editing, and sometimes other applications as well. Unfortunately, most image-editing software has been designed for graphic artists and designers who are willing to make an effort to learn how to use powerful but often arcane tools. With scanners becoming more popular, though, there has been movement in the industry toward easier-to-use image-editing software. Adobe's PhotoDeluxe and Ulead's PhotoImpact are good examples. More sophisticated users, on the other hand, should look for a bundle with a more robust image editor, such as Adobe Photoshop.

If you're new to image editing, you should plan to spend some time learning new concepts for both the scanning step and the image editing.

Gamma correction, essentially lets you modify contrast level at different levels of brightness. Changing the gamma setting can make a tremendous difference in an image, and understanding gamma correction will help you get better results at both your scanner and your image editor. You'll also want to experiment with the various other controls in your Twain driver to learn how they affect the image.

[Rev: 01/04/99] 11/10/97 © 1997-99 V/2-Com (Verhaart), P O Box 8415, Havelock North, New Zealand.