Adobe 13102498 User Guide - Page 65

58 Chapter 3: Opening and importing images Adobe® Photoshop® CS3 can open and import many types of graphic files. To work effectively, you should understand basic imaging concepts, and how to acquire, import, and resize images. Photoshop images About bitmap images Bitmap images-technically called raster images-use a rectangular grid of picture elements (pixels) to represent images. Each pixel is assigned a specific location and color value. 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 more efficiently 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 to high magnifications on-screen or if they are printed at a lower resolution than they were created for. 3:1 24:1 Example of a bitmap image at different levels of magnification Bitmap images sometimes require large amounts of storage space, and often need to be compressed to keep file sizes down when used in certain Creative Suite components. For instance, you compress an image file in its original application before you import it into a layout. Note: In Adobe Illustrator, you can create bitmap effects in your artwork using filters, effects, and graphic styles. See also "About vector graphics" on page 58 About vector graphics Vector graphics (sometimes called vector shapes or vector objects) are made up of lines and curves defined by mathematical objects called vectors, which describe an image according to its geometric characteristics.