QUESTION: How do you know whether you
should use a bitmap format as opposed to a vector format for
a particular graphic?
ANSWER: In many situations, vector
descriptions are more desirable than bitmap descriptions - for
However, when the graphic that you are talking about is a
photograph, bitmap is the way to go - because it is
difficult or impossible to create a vector description that
represents a photograph well.
- Vector descriptions are much smaller than bitmap descriptions.
- Graphics with vector descriptions look much better than graphics
with bitmap descriptions when you enlarge or reduce them.
Sometimes you don't have a choice about whether to use a bitmap
format or a vector format. That is: if you need to include
a graphic in a document that you are creating, and someone else
has already created the file for that graphic, you have to take
what you can get. Or, if you are creating the graphic yourself
and you don't have a large collection of graphics-software programs
at your disposal, you have to use whatever formats your
software programs can create.
(Of course, in some situations it is feasible to convert a graphic
from a bitmap format to a vector format and vice versa - but
file-format conversion is a topic unto itself and is certainly
outside the scope of our discussion here!)
Graphics on the Web:
If you are creating a graphic that will be used in a Web page,
you don't have a choice: you must use a bitmap format.
That's because today's Web browsers understand bitmaps but they don't
Generally, there are two graphics formats
used in Web pages:*
As we said earlier, JPEG and GIF are both bitmap formats.
- JPEG (generally, this format is used for photographs)
- GIF (generally, this format is used for graphics that are not photographs).
The fact that Web browsers don't understand vectors is a problem
for Web designers today. Why? Because it takes a long time to
download bitmap graphics from a Web site to a Web browser.
If graphics could be described in a vector format, it would take
less time to download graphic descriptions because the graphic
descriptions would be much smaller. Web designers spend a lot
of time and effort trying to minimize the sizes of the graphics
in their Web pages so that their site visitors won't navigate to
a different site because they've lost patience while waiting for the
graphics to download.
It is for this reason that several high-tech companies are now
working on developing a Web standard for vector graphics. This
standard is called "Scalable Vector Graphics" (SVG), and some
of the companies that are working on it are Adobe Systems, Quark,
Corel, Hewlett-Packard, and IBM. Learn about SVG at