In This Chapter
Understanding how paths and pixels work
Knowing the differences between paths and pixels
Determining when to use paths and when to use pixels
Using PostScript printing and paths
Being new to Illustrator typically means being new to paths. Paths are the heart and soul of Illustrator — its primary way to create graphics. Nearly all computer-generated graphics are either pixel-based or path-based (also known as vector-based — more on that later). Getting a firm grip on the differences between the two graphics types can help you create graphics of any type.
Pixel-based images (created in Adobe Photoshop as well as by scanners and digital cameras) use a fixed grid of tiny colored squares (kind of like a tiny mosaic tile) to create images on your screen. Your computer monitor’s resolution is a measure of how detailed an on-screen image can be, based on how many pixels the screen can provide per square inch. To give you an idea of how small these pixels are, every square inch of the average monitor contains up to 9,216 pixels. Even so, monitors have a relatively low resolution; they don’t use many pixels per inch compared with high-resolution printing, which can require 90,000 pixels in a square inch or more.
In spite of their astonishing quantity, pixels work just like mosaic tiles (or like the dots in a Seurat painting). Because images are a bit less distinct from farther away, putting squares of different colors together results in a smooth picture when seen from a distance; the individual squares are (in effect) invisible. The more squares used to create a square inch of the image (that is, the higher the resolution), the smoother and more realistic the picture is.
In addition to their staggeringly small size, the range of colors pixels can have is equally astonishing. A single pixel can display only one color at a time, but that color can be any of 16.7 million.
Path-based (often called vector-based) graphics are much simpler — and in some ways, easier to comprehend — than their pixel-based cousins. Think of an image in a coloring book: A shape is defined by a line. Inside the line, you can add color. By using this simple method of shapes and color, you can create just about any picture you can imagine. In Illustrator, the shapes can be any size and complexity, and the lines can be as thick or as thin as you want, or even invisible. And the shapes can be filled with an astonishing variety of colors, patterns, and gradients (even pixel-based images), but the same basic coloring-book principle applies.