Vector vs. Bitmap

1. Vector vs. Bitmap Monica Stoica, smonica@cs.bu.edu book used:the essential guide to computing by garrison walters

2. Bitmap • One meaning: an image that comprises a pattern of dots. • Second meaning: how an image is made – is created dot by dot for a specific size and resolution. Contrast with vector. • Bitmaps were first used in microcomputers by Apple in 1984 for fonts. Until Macintosh computers have been able to display one font only. The original Macintosh had 128K of memory, and exciting new capability given to people slowed computers down a lot… • Flash creates vector images while Photoshop and Paint Shop Pro create bitmaps

3. Vector Images • Vector images are the same as bitmap in that the final image is a bitmap –a series of dots. The difference is that vector images are built mathematical formulas rather than from a predetermined pattern of bits. • If you were to look at a vector image before it is drawn on the screen you would not see any bits, but rather something like:” to draw a capital I, start at the baseline and draw a line with thickness of x, for a distance of y.” • Since the result of the vector calculation must still be a pattern of bits, the formula translates its calculation for the resolution of the output devise – if it’s working with a 72dpi monitor, it will draw the letter on a grid with that scale.

4. Vector vs. Bitmap • Built from a formula • Can be scaled to different sizes for different resolutions – contrast with a bitmap which is created dot by dot for a specific resolution. • This formula approach provides a lot of flexibility – the formula works for a 12-point I as well as for a 15-point I – since you just change the value of y. If you want the letter bold, you can multiply the normal value of x by 1.5, or whatever.

5. Vector vs. Bitmap • The vector approach is more efficient with memory • The vector version of all the characters in Times Roman for example, will take more memory than a couple of fonts in the same typeface. But the vector approach will quickly be more efficient if there is a need for greater scalability than just few fonts.

6. What’ s used today? • On the net, objects in WebPages other than basic text and standard symbols are normally bitmaps – flash is about to change many of those though :). The reason for the current situation are: • Image are usually designed for computer monitors and won’t have to change resolution much • Bitmaps can be compressed quite easily – saves storage and bandwidth • Fonts are mainly vectors – today’s computer documents require a lot of flexibility and need to be scaled for the monitor and the printer.