Читать книгу Adobe Creative Cloud All-in-One For Dummies - Christopher Smith - Страница 99

You may wonder how images in Photoshop show subtle changes in color values. To create those smooth gradations from one color to the next, Photoshop takes advantage of pixels and anti-aliasing. Bitmap images (or raster images) are based on a grid of pixels, as shown in Figure 2-1. The grid is smaller or larger depending on the resolution of your image. The number of pixels along the height and width of a bitmap image are the pixel dimensions of an image, measured in pixels per inch (ppi). The more pixels per inch, the more detail in the image.

FIGURE 2-1: You can see the grid that makes up the pixel resolution of an image when you zoom in.

Unlike vector graphics (mathematically created paths), bitmap images can’t be scaled without losing detail. (See Figure 2-2 for an example of a bitmap image and a vector graphic.) Generally, you should use bitmap images at or close to the size you need. If you resize a bitmap image, it can become jagged on the edges of sharp objects. On the other hand, you can scale vector graphics and edit them without degrading sharp edges.

FIGURE 2-2: Bitmap versus vector.

Photoshop can work on both bitmap and vector art. (In the path line around the vector shape layer, notice that the path isn’t pixelated or broken down into a step pattern created by the pixels.) Combining the two technologies gives you, as a designer, incredible opportunities.

For information on changing and adjusting image resolution, see Chapter 6 of this minibook.