Vector graphics describe images using lines and curves, called vectors, that also include color and position properties as opposed to bitmap graphics which describe images using colored dots, called pixels, arranged within a grid. When you edit a vector graphic, you modify the properties of the lines and curves that describe its shape without changing the quality of its appearance. Therefore, vector graphics are resolution-independent, meaning they can be displayed on output devices of varying resolutions without losing any quality.

A vector object is a mathematical description of a geometric form. Vector paths are defined by points. Because they are described mathematically, vector paths do not show a degradation in quality when you make them larger or zoom in. The leaf in the illustration below is a collection of vector objects (fig. 1, below). Notice how smooth the leaf’s edges appear even when magnified.

Vector vs. Bitmap Graphics - an Introductory Guide for Clients and Designers One of the most common misunderstandings among both clients, and unfortunately many designers, is the difference between Vector and Bitmap (also known as Raster) graphics. This short whitepaper should serve as a reference to both client and designer; an attempt to articulate, in an understandable manner, the primary differences between these two graphic types and explore the areas where usage of each is most appropriate. A graphic design background is not required for understanding this paper; technical terminology is defined; however, an elementary understanding of computers and graphics is assumed.

It is worth mentioning in advance, because it is a critical point, that when we refer to Bitmap and Vector graphics, we are not referring to any particular file format or extension. Though file formats are typically responsible for saving one type of graphic or another, the distinction between Vector and Bitmap is independent of any assigned extension.

A graphic composed entirely of pixels each with its own color properties is ideal for photographic images where there are thousands, even millions of different colors. Complex fills, shading and gradient effects can easily be rendered. The Bitmap image offers as much freedom as an empty canvas.

In Bitmap graphics, there is an immutable connection between pixels and the image they compose. When a Bitmap graphic is saved, the computer is really saving an exact visual picture of the image: this pixel goes here and is this color; this pixel goes there and is that color, and so on and so on.

This connection is responsible for the effects seen when resizing a bitmap graphic. Given three image sizes - an original, one smaller, and one larger - each will naturally contain a different number of pixels. Pixels do not change sizes, but the image has. It takes more pixels to fill the volume of a larger space, fewer to fit into a smaller space. (fig 2, below).

Making an existing Bitmap graphic smaller is a process of reduction; pixels are removed from the image until it fits the new size. Computers are well equipped to perform this task. An image can be sized smaller repeatedly and still maintain the same quality, up until the point where there are not enough pixels available to reproduce the image clearly.

At any given size, a Bitmap graphic contains exactly the amount of information (pixels) required to display it. No more and no less. Increasing the size of a Bitmap Graphic is akin to pouring a drink from a smaller glass to a larger one. For the drink to occupy the full volume of the larger glass, we must add additional fluid. The original concoction is diluted, the flavor weakened.

In the same way, the computer must add additional information (pixels) to the original image to allow it to fill the new larger area. Since there is no source for this information, it must be interpolated based on what is currently available in the image. Because the computer is not especially skilled at guessing games, Bitmap images that have been scaled larger are frequently blurry. After extreme size increases, individual pixels “blocks” are more apparent (as though we held a magnifying glass up to it) and the image is said to be pixilated. Slight blurriness can be combated by sharpening the image with the filters provided within many graphic programs, but an enlarged image will never be as clear as the smaller original. This blurriness also occurs for the same reason any time a Bitmap graphic is manipulated, by rotating, skewing or distorting.

Vector Graphics

If we consider Bitmap graphics as being stored in a literal fashion, then Vector Graphics, stored representatively, are their opposites.

Rather than being composed of pixels, Vector graphics consist of points, lines, and curves which, when combined, can form complex objects (fig 3, below). These objects can be filled with solid colors, gradients, and even patterns.

Vector graphics are mathematical creations. For this reason, the programs that are used to create them save instructions on how the image should be drawn, rather than how it looks. This is the key difference between the two types of graphics. Because the computer has a description of how the image should look, it can be redrawn at any size, in any position, without losing any quality. A vector graphic resized to 5 times its original dimensions is simply reproduced, exactly, at the new size. It can also be freely manipulated without losing coherence, like a rubber band that can be stretched an infinite number of ways.

The price of this scaling flexibility is that Vector images must remain relatively simple in comparison to Bitmap images. It is impossible to render the nuances of a photographic image in a vector editor; as a result, illustrative vector graphics have a distinct look and feel, even when produced in detail. (fig 4, below)

However, Vector graphics are ideal for producing artwork which frequently needs to be presented in different sizes or colors. Logos especially fall into this category. A logo produced with a vector application can be blown up to fit on a billboard or scaled down to adorn a letterhead with no loss of quality.