Xerox Fiery color server User Manual page 107

A
A-15 Desktop Color Primer
The amount of data found in a raster image depends on its resolution and bit depth.
The resolution of a raster describes the compactness of the pixels and is specified in
pixels per inch (ppi). The bit depth is the number of bits of information assigned to
each pixel. Black and white raster images require only one bit of information per pixel.
Grayscale images require 8 bits per pixel. For photographic quality color, 24 bits of
RGB color information are required per pixel, yielding 256 levels of red, green, and
blue. For CMYK images, 32 bits per pixel are required.
When printing raster artwork, the quality of the output depends on the resolution of
the source raster. If the raster resolution is too low, individual pixels become visible in
the printed output as small squares. This effect is sometimes called "pixelation."
In vector graphics, picture objects are defined mathematically as lines or curves
between points—hence the term "vector" (see example b). Picture elements can have
solid, gradient, or patterned color fills. Vector artwork is created in illustration and
drawing applications, such as Illustrator and CorelDRAW. Page layout applications,
such as QuarkXPress, also allow you to create simple vector artwork with their drawing
tools. PostScript fonts are vector-based, as well.
a b
Vector artwork is resolution-independent; it can be scaled to any size and resolution
without danger of pixels becoming visible in printed output.