Computer graphics fall into two main types: vector
graphics and bitmap images. We'll make a quick
comparison of the two to help you understand which is
more appropriate for your artwork. It boils down to the
kind of artwork you're preparing and what you intend
to do with it.
Vector vs. Bitmap
Vector graphics
are made up of shapes defined by mathematical
expressions. A vector graphic has crisp, smooth
lines and is resolution-independent—that is, it can be
rescaled to any size or displayed onscreen at any
resolution without losing the clarity of its lines.
Bitmap images
(also called raster images) are based on a
grid of small squares known as pixels. Each pixel has a
specific location and color value assigned to it. Bitmap
graphics can represent subtle gradations of shade and
color. A disadvantage of bitmaps is that they represent a
fixed number of pixels, so they can appear jagged and
lose detail if they are rescaled or displayed onscreen at a
higher resolution.
Which graphic type should you use?
So which type do you need? It depends on what you're
trying to do:
• Vector graphics are crisp at any size or resolution, so
they're well suited for line art, type (especially small
type), and graphics that may need to be scaled, such as
logos and maps. Vectors also produce more compact
files than bitmaps, so they're quicker to open or
download on systems with limited memory or lowbandwidth
connections.
• Bitmap images can represent rich and subtle gradations
of shade and color, so they're appropriate for
artwork created in painting programs and for
continuous-tone images such as photographs. You
might also want to convert vectors to bitmaps to apply
distortion filters or other special effects to them.
Drawing programs such as Adobe® Illustrator® are
ideal for creating vector graphics. Bitmap images are
generally created using graphics programs such as
Adobe Photoshop®. Both Illustrator and Photoshop
can rasterize your vectors into bitmaps.
What's next for graphics on the Web?
Most graphics on the Web today are in bitmap formats,
such as GIF, JPEG, and PNG. Up until now, the only
vector formats practical for the Web have been proprietary
standards, such as Flash (SWF)—but a new openstandard
format called Scalable Vector Graphics (SVG)
is emerging.
SVG will let Web developers use high-quality vector
fonts and graphics that look great at any size or
resolution and that incorporate sophisticated elements
such as gradients and animation. Imagine being able to
zoom into a map on the Web! And SVG vector descriptions
are embedded in the HTML code, so developers
can put interactivity, such as rollover highlighting, right
in the artwork.
Illustrator 9.0 exports to both SVG and SWF vector
formats. You can even define SVG interactivity for your
artwork within Illustrator.