Computer graphics falls into two main categories--bitmap and vector. Understanding the difference between the two categories helps as you create, edit, and import artwork.
Bitmap Images
! Bitmap images--technically called raster images--use a grid of colors 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. ! Bitmap images are the most common electronic medium for continuous-tone images, such as photographs or digital paintings, because they can represent subtle gradations of shades and color.
Bitmap images are resolution-dependent--that is, they contain a fixed number of pixels. As a result, they can lose detail and appear jagged if they are scaled onscreen or if they are printed at a lower resolution than they were created for.
Bitmap images are good for reproducing subtle gradations of color, as in
photographs. They can have jagged edges when printed at too large a size or displayed at too high a magnification.
Vector graphics
! Vector graphics are made up of lines and curves defined by mathematical objects called ‘vectors’. Vectors describe an image according to its 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.
! Vector graphics are resolution-independent--that is, they can be scaled to any size and printed at any resolution without losing detail or clarity. As a result, vector graphics are the best choice for representing bold graphics that must retain crisp lines when scaled to various sizes--for example, logos.
! Vector graphics are good for reproducing crisp outlines, as in logos or
illustrations.
! They can be printed or displayed at any resolution without losing detail.
Because computer monitors represent images by displaying them on a grid, both vector and bitmap data is displayed as pixels on-screen.
