tailieunhanh - How to Do Everything With Your Scanner- P10

How to Do Everything With Your Scanner- P10: 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. | CHAPTER 2 How Scanning Technology Works 29 CMYK Color Channels A scanner or device with a 32-bit depth is capable of creating images containing four layers of 8-bit pixels or four different color channels. These are called CMYK 2 channels for the primary colors of cyan magenta yellow and black. By combining these four-color channels a device can create million colors. Cyan is a sort of aqua-blue color. The K is used to represent black in the acronym because a letter B could be erroneously assumed to stand for the color blue. How a Scanner Interprets Pixels There is actually no such thing as a color scanner A 24-bit scanner reads each pixel in a color image and interprets it as one of 256 shades of gray. In other words you re actually capturing a color image as a grayscale image every time you scan. Your monitor and computer graphics card generate the color that you see on your screen when it interprets the scanner s grayscale. Similarly the color you get from your printer is a product of the printer s software interpreting the grayscale not of information conveyed directly by your scanner. NOTE Your computer graphics card determines the detail and depth of color rendered by your monitor. The graphics card is an expansion board within your computer that converts images contained inside your computer to electronic signals that can be interpreted by your monitor. The card contains memory to store color data information. Decide How Much Bit Depth You Actually Require Nearly all scanners on the market today have the minimum 24-bit depth necessary to create color images. You also see scanners advertising 30- 40- or even 46-bit capacity. Are these better than 24-bit capacity The general rule is that the more bits used to store a color the more colors can be stored. The higher the bit levels the truer to the original the scan will be. But the human eye can discern only so many colors. A 24-bit scanner can actually combine 256 shades of gray to capture about .