TAILIEUCHUNG - How to Do Everything With Your Scanner- P27

How to Do Everything With Your Scanner- P27: My thanks to the terrifically creative and knowledgeable staff at Osborne, particularly acquisitions editor Megg Bonar and acquisitions coordinator Alissa Larson for their responsiveness and flexibility. Special thanks to technical editor Steve Bain, not only for his insight and attentiveness to accuracy, but also for actively coming up with many ideas for content. | 114 How to Do Everything with Your Scanner How to Scan Previously Half-Toned Images When you scan a previously half-toned image you re working off a medium that has less data than the original photograph. Some of the valuable data was discarded at the time the photo was converted by the half-toning process. Scanning at lower resolutions or selecting an optimized palette option often yields good results when scanning previously half-toned images. You can also opt to capture the previously half-toned image as black and white following the guidelines for such images given earlier in this chapter. Scanning Text and Images that Contain Text Text is a different animal to scan than an original that contains both images and text. Most scanners have separate settings for scanning both types of originals. Text is scanned using optical character recognition OCR software. This topic of scanning text is covered in depth in Chapter 13. How Interpolation Works Interpolation is a process that s used when you increase or decrease the size of an image or change its color depth. When an image is enlarged the density of pixels per inch decreases making the color gradations between the pixels more noticeable. This also makes the edges of the image jagged. Interpolation is a process performed by your software that makes extra pixels using a mathematical algorithm to reproduce the existing pixels. Interpolation looks at the existing pixels and carefully creates matching ones to fill the area. If one pixel is light gray and another is dark gray interpolation creates a medium gray pixel to fill the intervening area. Most scanner software applications include a feature that allows you to apply interpolation to your scanned images. When you purchase a scanner and want to know its resolution capabilities be sure you re distinguishing between standard and interpolated resolution. They re two different measurements. Chapter 7 Troubleshooting Tips and Tricks Copyright 2001 by The McGraw-Hill .

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