Chapter 5. Getting to the Point of Vector Graphics

Unlike raster images, which use bitmaps in a grid of colors known as pixels, vector graphics use mathematical formulas to define the shape of lines and curves. Adobe built an application around vector graphics Adobe Illustrator, first demonstrated at the January 1987 Macworld Expo. At its heart was the Pen tool a tool that a designer could use to visually create the same curves described in mathematical formulas.

In the early days of Illustrator and Photoshop (released in 1990), the chasm between such vector programs as Illustrator and pixel programs as Photoshop was huge. Vector paths and pixel images never mixed. To modify a scanned image, you had to work in Photoshop. To set PostScript type or create a company logo, you had to use Illustrator. Page layout programs such as PageMaker (later InDesign) were the only places where you could combine vector paths and pixels. But even then, the two different formats never interacted with each other.

These days the boundaries between the two formats have blurred. Illustrator, Photoshop, and InDesign all have Pen and other tools that let you create and work with vector paths. They also have features to soften vector paths into pixels and add pixel drop shadows to paths. This chapter explains the different features for working with vector tools in each of the CS2 applications as well as the cross-suite similarities. It also looks at the formats used to save vector information and how to transfer paths between the programs.

Behind the Scenes: The Father of Vector Curves

What is the link between vector graphics and a Renault? The answer is Pierre Etienne Bézier, a French mathematician who was an engineer for the Renault car corporation. In the early sixties, Bézier was working on a new mathematical method to describe the shape of curves. While it is rather easy to define a straight line using x and y coordinates, a curve is more complicated. Bézier created a system that defines the shape of a curve using the coordinates of a tangent line that extends along the curve. This system makes it possible to define curves with mathematical precision using just a few coordinates to show the origin of the tangent and the length and position of its start and end points. (This sounds a lot more complicated than it really is.) What made this system so important was that a simple straight line could be used to define the shape of a curve.

It was this technology of "Bézier curves," as they later became known, that was one of the important foundations in PostScript the printer language created by Adobe Systems founders John Warnock and Chuck Geschke. Using mathematical expressions, PostScript was able to generate font descriptions of any size and shape without using hand-drawn, bitmapped characters. The PostScript language, created in 1985, was the first product of Adobe Systems.