Chapter 16: Monitors and Displays^387
Raster Graphics
A raster graphic, which is also known as a bit-mapped graphic, is a two-dimensional
array of pixels that is drawn by assigning a value to eachx(horizontal) andy(vertical)
pixel position on the screen. This is the most common technique used to create the image
on the CRT display. Colors used in raster graphics can be found in a Color Lookup Table
(CLUT), which contains the supported color depth subset of the entire color palette of the
video graphic standard in use.
Raster graphics are formed by patterns of pixels on the monitor’s screen. A raster
graphic is made up of a matrix of on and off pixels. For example, to draw the letterHon
the screen, a pattern of pixels must be illuminated, as is illustrated in Figure 16-10. As
shown, raster graphics are by nature blocky images.
This is even more apparent in images that have curved or sloping edges, like the diag-
onal line shown in Figure 16-11. A diagonal line drawn on a raster display is a problem
because of the row and column orientation of the pixels. Diagonals often have a jagged
look resembling a staircase, such as the exaggerated example in Figure 16-11. This effect
is minimized as the resolution of the display increases. Another technique used to mini-
mizethejaggednessoftheimageisantialiasing,whichshadesthepixelsalongtheedgeof
the image to minimize the sharp contrast of the image to the background.
Figure 16-10. A text character created using raster graphics