1: What is a Bitmap Graphic?
>> Part 2: What is a Vector Graphic?
Part 3: Comparing Bitmaps and Vector
2: What is a vector graphic?
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
versions of the same two points (A & B). Only the math
that describes how to get from A to B (the path) is different.
points and the path between them can make a simple shape.
enough points and you make things like the Freerange Stock
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.
blue line is a graph of the little equation y=(x squared)
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.
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
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.
the Freerange vector logo, viewed at 100% on screen.
a wingtip from the same logo, blown up to 1600% on screen.
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.
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...).
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...).
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.
is an "F" as it normally appears on screen - nothing
the "F" after Converted to Paths in an illustration
program. Now it's just a vector shape...
it can be edited just like any other vector shape - drag the
points around to redefine the path.
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.
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
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