rograms like ColorWorks and PhotoShop are both bitmap applications, treating the images you work with as a fixed-size resource made up of a fixed number of dots, or pixels. Once a line or curve or piece of text has been 'committed' to the canvas you can not go back and change it without undoing and starting over again.

Also, since the information in a picture is represented by dots, you cannot enlarge the image without exaggerating the effect of these dots and making the picture look jagged. One advantage of using this scheme is that scanned photographs are always represented as bitmaps (the detail in the average photograph is way too complex to be represented as vectors), so if you want to work with these items you'll need a bitmap based program. Another advantage is the mathematical functions that can be performed on a bitmap, such as averaging the pixels to create a blur, or edge detection routines that emboss.

Vector based applications such as Corel Draw and LogoArt treat images as collections of vectors and shapes. A line would have a starting point, direction and length, a rectangle would have a starting point, width and height, circles would have a center and radius, and so on. After drawing a rectangle you can go back and change its width and height, bring it to the foreground or send it to the background, even after other shapes had been drawn on top of it later. When saved to file, vector images also take up less disk space, since, for example in the case of a rectangle, the program is only storing four numbers no matter what its size: the x and y starting point, plus the width and height. In comparison, a bitmap application would have to store color information for the 10,000 pixels that make up a 100x100 pixel rectangle.

Another advantage of Vector based applications is that you can re-size the final image to be as large or as small as you like and never obscure the detail with jagged edges.

Chris Wenham is a freelance web designer, writer and Englishman who now lives in Endicott, NY. In the past he has written comedy, sci-fi, Pascal, Rexx, HTML and Gibberish. He has been using OS/2 exclusively for the past 2 years.

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