 |
|
| Computer graphics fall into two main
categories—bitmap images and vector graphics. Understanding the difference
between the two will help as you create and edit digital images. Samples of Bitmap Images and Vector Images Photoshop and other paint and image-editing programs generate bitmap images, also called raster images. Bitmap images use a grid (the bitmap or raster) of small squares known as pixels to represent images. Each pixel is assigned a specific location and color value. For example, a bicycle tire in a bitmap image is made up of a mosaic of pixels in that location. When working with bitmap images, you edit pixels rather than objects or shapes. A bitmap image is resolution-dependent—that is, it contains a fixed number of pixels to represent its image data. As a result, a bitmap image can lose detail and appear jagged if viewed at a high magnification on-screen or printed at too low a resolution. Bitmap images are the best choice for representing subtle gradations of shades and color—for example, in photographs or painted images. Drawing programs such as Adobe Illustrator® create vector graphics, made of lines and curves defined by mathematical objects called vectors. Vectors describe graphics according to their geometric characteristics. For example, a bicycle tire in a vector graphic is made up of a mathematical definition of a circle drawn with a certain radius, set at a specific location, and filled with a specific color. You can move, resize, or change the color of the tire without losing the quality of the graphic. A vector graphic is resolution-independent — that is, it can be scaled to any size and printed on any output device at any resolution without losing its detail or clarity. As a result, vector graphics are the best choice for type (especially small type) and bold graphics that must retain crisp lines when scaled to various sizes—for example, logos. Because computer monitors represent images by displaying them on a grid, both vector and bitmap images are displayed as pixels on-screen.
| |||