Pixels, Paths, and

The vast majority of the artwork with which you work (or play) in Photoshop is raster artwork. Raster imagery consists of uniformly sized squares of color (pixels), placed in rows and columns (the raster). Digital photos, scanned images, and just about anything that you put on a layer in Photoshop consists of pixels. While you edit the image, you're changing the color of the individual pixels, sometimes in subtle ways and sometimes in dramatic ways.

Vector artwork is a horse of another color. Rather than pixels, vector art consists of a mathematically defined path to which you add color. In a dedicated vector art program, such as Adobe Illustrator, the path produces the shape of the object, and you add color along the path (stroke) or within the path (fill) or both to make the shape become an object. Photoshop simulates vector artwork using vector paths on shape layers to hide parts of a layer, so you can fill the "shape" but not add a stroke to the path. (A shape layer is filled with a specific color, gradient, or pattern; and a vector mask determines what part of the layer is visible.) Remember that you can use layer styles in conjunction with shape layers to simulate strokes and other effects.

Figure 11-1 shows a fine example of vector artwork. Observe that each element in the image consists of a single color. Each section of the image is easily identifiable as an individual object, consisting of a specific color. (Remember, though, that vector objects can be filled with gradients rather than color.)

Each element in the artwork is defined by its path, which consists of a number of path segments. In Figure 11-2, you see the path that defines the woman's hair. (You read about the anatomy of a path later in this chapter, in the section "Understanding paths.")

©PhotoSpin, PhotoSpin image #PI009008

Figure 11-1: Each element in vector art has a single specific color.

©PhotoSpin, PhotoSpin image #PI009008

Figure 11-1: Each element in vector art has a single specific color.

Figure 11- 2: Paths define the outline of an object — the woman's hair in this case.

When artwork is defined by pixels, the little square corners of the individual pixels can be noticeable along curves and diagonal lines. With vector artwork, the path is sharp, and the edges are well defined. However, to truly get the best appearance from vector art or vector type, the artwork must be printed to a PostScript-capable device, such as a laser printer. PostScript is a page-description language that takes advantage of the mathematical descriptions of vector art. When you print to an inkjet printer, the vector art is converted to pixels. If you print to such a non-PostScript device, use a high image resolution for best output — 300 pixels per inch (ppi) is usually good.

A vector path can be scaled (changed in size) almost infinitely without losing its appearance. A vector logo can be used for both a business card and a billboard without loss of quality because the path is mathematically scaled before the stroke or fill is added. Raster art, on the other hand, can be severely degraded by scaling. For a simple demonstration of the difference between scaling raster art and scaling vector art, see Figure 11-3.

Raster, from small to large

Raster, from large to small

Vector, from small to large Vector, from large to small

Figure 11-3: Using text as an example shows the advantage of vector artwork when scaling.

Type in Photoshop is vector-based: That is, it's created with paths. Objects in Photoshop, such as circles and squares that you create with vector paths, can also be scaled as vector artwork. The paths are recalculated to their new size and retain their crisp, sharp edges.

Understanding Adobe Photoshop Features You Will Use

Understanding Adobe Photoshop Features You Will Use

Adobe Photoshop can be a complex tool only because you can do so much with it, however for in this video series, we're going to keep it as simple as possible. In fact, in this video you'll see an overview of the few tools and Adobe Photoshop features we will use. When you see this video, you'll see how you can do so much with so few features, but you'll learn how to use them in depth in the future videos.

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