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Part 1: What is a Bitmap Graphic?
>> Part 2: What is a Vector Graphic?
Part 3: Comparing Bitmaps and Vector Graphics

Part 2: What is a vector graphic?

In regards to this discussion, a vector graphic is one in which the shape or path of a line is defined by a bit of math. Vector graphics are basically points connected by lines of various shapes, filled with solid or gradient colors. So it's point A, connected to point B by a line of some shape, with the shape of that line defined by a little mathematical description. More points and more lines can make more complex shapes. The line that defines the vector shape is referred to as the path. (See Illustration 5).

ILLUSTRATION 5:


Two versions of the same two points (A & B). Only the math that describes how to get from A to B (the path) is different. Five points and the path between them can make a simple shape. Use enough points and you make things like the Freerange Stock logo.

Drawing a shape with math? What's that supposed to mean? Well, if we think back to our algebra classes, lines and curves can be drawn in an X and Y coordinate space by graphing equations. (See Illustration 6.) In Illustration 6, a graceful curved line (parabola) is drawn simply by graphing the equation y = (x squared). By making the math more complicated, you can define more nuanced shapes. And there is no grid to worry about: as you make y = (x squared) much larger or much smaller, the line of the parabola is still perfectly defined. Its resolution is infinite.

ILLUSTRATION 6:
The blue line is a graph of the little equation y=(x squared)

Basic geometric shapes like lines, circles, ovals, squares, rectangles and polygons with any number of sides, are mathematically simple and are a good starting point for vector graphics.

Images made up of shapes, like line drawings and illustrations and logos, are often well suited for vector formats. Images with dense, differing colors, like photographic images, are NOT well suited to vector graphic formats.

Some advantages of vector graphics:
There are (at least) three very neat things about vector graphics:

- First, the file sizes are usually very small - rather that describing the many, many squares in a bitmap, it is only necessary to describe the math involved in recreating the image. For example, the Freerange Stock logo file used as the basis for the third panel of Illustration 5 above is only 36KB.

- Second, they have infinite resolution - no matter how large you expand or how small you contract the image, the math creating it holds up and it will always show smooth, clear edges and details. The little 36KB logo file mentioned above can be printed at ANY size (see Illustration 7) and will look great.

ILLUSTRATION 7:

Here's the Freerange vector logo, viewed at 100% on screen. Here's a wingtip from the same logo, blown up to 1600% on screen. Still sharp.

- Third, the image remains editable as long as it remains in a vector format - any program that can understand the math will open the graphic can and modify its shapes, arrangements and colors. The points along the path can be moved around, and, when selected, have little arms sticking out of them - drag the arm and it changes the shape of the path as it passes through that point.

Once a "universal" version (usually an .eps file) of a graphic or a logo is PROPERLY originated, it can be used by may people and many different software packages. You do not have to recreate images in each application - this saves time and allows you to distribute and have greater control over your logo/brand/whatever. This can also be a big mess (see disadvantages below...).

Some disadvantages of vector graphics:
- The primary thing to keep in mind with vectors is this: Vector formats are NOT well suited to photographic images. The many colors and complexity necessitated by representing photographic subjects quickly overwhelms the formats. This isn't necessarily a disadvantage - it's just not something for which vector formats are well suited. Similarly, for advanced manipulation and complex colorings and lighting effects, you would need to rasterize (defined in Part 3) the vector into a bitmap and go from there.

- Vector formats aren't as universally interoperable as bitmaps. Even "universal" formats like .eps are often misused and misunderstood, so trying to give a vector graphic to your friend who doesn't have the same software can be a struggle. (Especially, in my experience, using Corel products.) Without caution and some expertise, your logo or graphic can be distorted, have the wrong fonts, be the wrong color, be uselessly low resolution or be missing entirely. On the other hand, once it's worked out properly it can be an advantage (see above...).

Vector graphics we use everyday: Type!
Did you know that we all use vector graphics everyday? Fonts are vector graphics shaped like letters, and they illustrate the behavior of vectors very well. First, small file size - an entire font, composed of many letters, numbers and symbols, is a small file that can easily be downloaded or emailed. Second, scalability and resolution independence - type can be set to any size and it never starts to look chunky. (That is, if your fonts are properly installed and used. There are cases where fonts will look chunky and have stair-stepped edges, but that's another topic.) So when you install and use a font, you are working with vector graphics - some programs (mostly the illustration programs mentioned below, like Illustrator and Freehand) even allow you to convert these text shapes into editable shapes or paths. Once converted to paths (see Illustration 8), you can modify the shape of the letters or fiddle with them anyway you like.

ILLUSTRATION 8:


This is an "F" as it normally appears on screen - nothing unusual. Here's the "F" after Converted to Paths in an illustration program. Now it's just a vector shape... And it can be edited just like any other vector shape - drag the points around to redefine the path.

Programs that use vector graphics:
Many programs can use vector graphics in one form or another. Page layout programs like Quark XPress and Adobe InDesign can import, place, scale and distort (but not create or otherwise modify) vector graphics, usually in the forms of an .eps file. And they use text, which, we just noted, is basically a vector graphic. Several other applications are also capable of using the files, but not creating them. Vector graphics are usually created in programs called illustration programs, like Adobe Illustrator, Adobe (formerly Macromedia) Freehand or Corel Draw. These are the programs that allow you to start with a blank document, draw or design what you want, and then export a completed .eps file for use elsewhere.

Vector formats:
Some of the most prominent vector formats are EPS (Encapsulated Post Script - .eps), Adobe Illustrator (.ai), Adobe (formerly Macromedia) Freehand (.FHx). One a side note Adobe (formerly Macromedia) Flash files are mostly vector data.

Formats that can deal with both bitmaps and vector information:
Recent Photoshop versions use a .psd file that can include vector layers (like text and shapes and paths). Adobe Acrobat's Portable Document Format (.pdf) files can contain bitmap images and vector data in many different forms. The .eps format is also capable of holding both vector and bitmap data, which is why this format can get messy as an interoperable standard for vector files. On a side note, the .eps file is basically the same file that a Post Script laser printer uses. (Remember, EPS is Encapsulated Post Script, and many laser printers use the Post Script language to format printed pages.) EPS/Post Script was developed by Adobe, and is also the basis of Adobe's now-universal PDF format.


Move on to Part 3: Comparing Bitmaps and Vector Graphics

 


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