Thursday, November 17, 2005

1600 x 1200? No Problem!

Vector Graphics and their applications

by Paul Reny (Class of '05)

Ever find an image online somewhere, and think “Wow, that would look good as my desktop background!” only to find that alas, when the image is stretched to cover your beautiful 1600 x 1200 pixel display, it is distorted and blocky. Well, that problem is easily solved with vector graphics. Distorted images be gone, vector graphics are the way of the future, despite the fact that they are still somewhat in their infancy.

Vector graphics, also known as object oriented graphics, are images that are completely described using mathematical definitions. They are constructed using mathematical formulas describing placement, shapes, and colors. Unlike Bitmap images, vector graphics contain shapes, lines, text, and curves, which all together form a picture. Each individual line is made up of a few control points that are connected using Bezier curves. A Bezier curve in its most common form is a simple cubic equation that can be used in any number of ways. Originally developed in 1970 by Pierre Bezier for computer aided design, it has become the foundation of the entire Adobe PostScript drawing model. Using the minimal amount of control points to draw curves, this model is a very space efficient way of drawing images.

In addition to the simplicity with which they are drawn, altering vector graphics is a very simple process, as the shapes and components within them can easily be ungrouped and edited separately. Due to their use of mathematical formulas, vector graphics based images are easily scalable without any loss in quality, up to 6400%. This is a vast improvement over bitmap images, where the slightest enlargement starts to distort the image greatly, even given recent improvements in anti-aliasing. Therefore vector based images are ideal for logos, maps and other objects which are resized frequently. However, due to the nature of the way data is stored in vector graphics based images, they are not well suited to complex images such as pictures. The lack of well defined shapes and lines makes it very difficult to create vector graphics based images from photograph type images. This is the one major shortcoming that vector based graphics images have. An additional minor problem with vector based images is that there is not one uniform file type, such as GIF or JPEG file types for bitmaps, which is used for all vector graphics. Fortunately, it is relatively easy to convert vector based images into bitmaps, although much more difficult to do the opposite conversion.

Since vector based images only need to store instructions for drawing an image, i.e. the data for the few points of the Bezier curves, and not data for each individual pixel, a vector graphics file is significantly smaller than a bitmap file. Often, vector data stored in EPS format, which includes a bitmap preview in addition to the Bezier data, is actually smaller than th e preview data. Other vector graphics formats are PICT, EPS, and WMF, in addition to PostScript and TrueType fonts. Common programs used to draw vector graphics images are Adobe Illustrator, Corel Draw, and Macromedia FreeHand. While bitmaps will continue to dominate the photo image industry, vector graphics are by far a superior choice for simple, scalable, compact size images.


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