Page 18 - Enhancing CAD Drawings with Photoshop

4386.book Page 1 Monday, November 15, 2004 3:27 PM

Chapter 1

The Basics

Color is represented by computers in unique ways. The relationship between bit depth and storage
space is important. Photoshop’s layer, paint, and filter tools have a wealth of features and options.
You must be at least familiar with just a few of these basics before you can start to work creatively in
Photoshop.
Fundamentals such as anti-aliasing, vectors, and additive versus subtractive color are also basic
concepts that you need to know to help build a solid foundation for a broad understanding of digital
imaging.
If you are familiar with Photoshop, you can go through this chapter quickly, skipping sections that
present material you already know well. However, be sure to understand the basics before you dive
into tutorials in the following chapters.
◆ Color vs. Number
◆ Understanding Modes, Bits, and Channels

◆ Using Layers
◆ Painting, Adjusting, and Filtering
◆ Text, Shapes, and Paths
◆ Sizing and Transforming

Color vs. Number
Computers store data in two basic ways: in colors and in numbers. Ultimately, computers reduce
everything to ones and zeros, so you could say that, in the end, computer operating systems simply
crunch numbers. However, at a higher level, what that data represents becomes important because
the data relates to what you can do with it in a program.
When data fundamentally represents numbers, a program can easily apply math to manipulate
the data set. All computer-aided design (CAD) programs are vector based, meaning they fundamen-
tally manipulate numbers behind the scenes.
The term vector literally refers to a mathematical object that is defined at a point in space (implying
a coordinate system), with a given magnitude (shown by the length of a line segment) and direction
(indicated by an arrowhead at the end of the line). You might have dim memories of vectors from
those math classes you once took in school. So what does this have to do with CAD anyway?
In a way, vectors have everything to do with CAD, because CAD is based on points, lines, angles,
coordinate systems, and so on. The word vector was sort of chosen as a mascot for this type of euclidean