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 two reasons:

  1. Generally, vector descriptions are smaller than bitmap descriptions. That is: a vector description of a graphic typically requires less code than a bitmap description of that same graphic.

  2. Graphics with vector descriptions look better than graphics with bitmap descriptions when you enlarge or reduce them.
However, when the graphic you're talking about is a photograph, bitmap is the way to go, because it is difficult to create a vector description that is a good representation of a photograph.

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 or vice versa, but file-format conversion is a topic unto itself and is outside the scope of our discussion here.