ww.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Protocols Protocols Figure 2-16a My daughter, Cristina Figure 2-16b Cristina's eye showing pixels image can be further compressed, but the point is that the number of bits required to reconstruct a high-quality image is dramatically reduced by using JPEG. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Protocols Chapter 2 More About Compression Compression schemes do a good job of compressing and faithfully recon- stituting images, particularly when the image being compressed is a photograph or video clip. To understand the dynamics of this relation- ship, let's take a moment to consider what it takes to create a digital photograph displayed on a computer screen. A laptop computer display is often referred to as being "640 by 480," "800 by 600," or "1024 by 768." These numbers refer to the number of pic- ture elements, more commonly called pixels, that make up the display. Look closely at the screen of your computer and you will find that it is made up of thousands of tiny spots of light (the pixels), each of which can take on whatever characteristics are required to correctly and faithfully paint the image on the screen. These characteristics include color com- ponents (sometimes called chrominance), black and white components (sometimes called luminance), brightness (the intensity of the signal), and hue (the actual wavelength of the color). These characteristics are important in video and digital imaging systems because they determine the quality of the final image. The image, then, is a mosaic of light; the "tiles" that make up the mosaic are light-emitting diodes that create the proper light at each pixel location. Each pixel has a red, green, and blue "light generator," as sh