新：求The ERDAS Field Guide第四，五章内容

Chapter 4 Image Display
本章教学要求：1、重点：RGB & Displaying Raster Layers 部分
2 、Using the Viewer 部分，结合实习1
Introduction
This section defines some important terms that are relevant to image display. This may differ from other systems, such as Microsoft Windows NT.
The display hardware contains the memory that is used to produce the image. This hardware determines which types of displays are available (e.g., true color or pseudo color) and the pixel depth (e.g., 8-bit or 24-bit).

Display Memory Size
• display resolution—the number of pixels that can be viewed on the display screen.
• the number of bits for each pixel or pixel depth.

Pixel（file pixel & display pixel）
• the data file value(s) for one data unit in an image
• one grid location on a display or printout
To display an image, a file pixel that consists of one or more numbers must be transformed into a display pixel with properties tha