Adobe Illustrator CS2 Tutorial
University of Texas at Austin
School of Information IT Lab
Jin Wu Fall, 2006
Illustrator is a vector-based imaging program. Unlike PhotoShop, which deals in
pixels (raster images), this one deals in lines and algorithms for various shapes.
It functions by generating curved paths connected by modifiable anchor points.
These anchors, with their handles, are ultimately editable and never "leave" the
structure of the file.
What are vector graphics?
Computer graphics fall into two main categories -- vector graphics and bitmap
images. Understanding the difference between the two helps you create, edit,
and import artwork.
In Illustrator, the type of graphic image can have important effects on your
workflow. For example, some file formats only support bitmap images and others
only vector graphics. Graphic image types are particularly important when
importing or exporting graphic images to and from Illustrator. For example, linked
bitmap images cannot be edited in Illustrator. Graphic formats also affect how
commands and filters can be applied to images; some filters in Illustrator will only
work with bitmap images.
Adobe Illustrator creates vector graphics made of lines and curves defined by
mathematical objects called vectors. Vectors describe graphics according to their
geometric characteristics. For example, a bicycle tire in a vector graphic is made
up of a mathematical definition of a circle drawn with a certain radius, set at a
specific location, and filled with a specific color. You can move, resize, or change
the color of the tire without losing the quality of the graphic.
A vector graphic is resolution-independent -- that is, it can be scaled to any size
and printed on any output device at any resolution without losing its detail or
clarity. As a result, vector graphics are the best choice for type (especially small
type) and bold graphics that must retain crisp lines when scaled to various sizes -
- for example, logos.