Graphics in Your CS5 Documents
You can create graphics manually by making marks on a page or create them electronically using software like Adobe Creative Suite 5. A graphic can be an image, a drawing, or a vector object. Graphics can be displayed in many formats, such as on a computer screen, projected on a wall, or printed in a magazine or book.
Computer graphics come in many forms, grouped by the way they’re created electronically. Bitmap and vector graphics are formed in different ways to achieve the result you use in your documents.
Bitmap images are pictures made up of many tiny squares, or bits, on an invisible grid. When these dots are next to each other, the picture is formed, depending on where and how the colors are arranged on the grid. If you zoom in far enough, you can even see the blocky dots, or pixels, that make up the image.
At 400 percent zoom, notice how the image is made of large squares. However, when you look at most bitmap images at their true sizes, you don’t even see pixels.
The bitmap is a useful way to display photographs and apply effects to text. When you paint or create detailed graphics, you frequently use bitmaps. However, remember that images can lose quality if you scale them (change their size). Resizing pixels causes the image to lose definition and quality. Most problems occur when an image is enlarged. Common kinds of bitmap files are BMP, GIF, JPEG, PICT, and TIFF.
A vector image (or graphic or drawing) is quite different from a bitmap image. A vector image is created by a series of mathematical calculations or code that describes how the image should be formed. These calculations tell the computer how the lines should display and render on the page.
Vector images are usually smaller files than bitmap graphics because the mathematical information required to make the calculations to create the vector image is usually smaller in file size than the information that it takes to make up each pixel of a bitmap. Compression can lessen a bitmap’s file size, but they’re usually larger and slower to display.
For this reason and because vectors are helpful in scaling an image, these graphics are well suited for the web.
Scaling is easy to do when you’re using vectors because the program needs to modify the calculations only slightly to make the image larger or smaller. This means the file size won’t change, and the scaling is very quick. You can scale the image on a web page to fill the browser window, whatever size it is, or make the image huge for a large banner. The quality doesn’t degrade, and the file size remains the same.
Vectors aren’t always perfect for the web. A bitmap is frequently the best way to display a photograph because if you change a bitmap image into a vector drawing (which is possible by using tools), you lose too much of the photograph’s detail for many purposes. Also, certain effects, such as the drop shadow, are best displayed as bitmap images.