2. Vector image

Vector images can be resized as much as you like, and still seem just as crisp and unpixellated as the original. We call this property resolution independence, as the quality of the image is independent of the image resolution.

A good example of this is the fonts and typefaces used by your computer. The characters in a typeface are stored as a single vector image. When you increase the font size in a word processor, it scales up the vector image to match. For example:

 small        bigger      bigger still

Vector images work this way because they don't store pixel data, like bitmap images do. Instead, they store a set of instructions of how to draw the shape. The computer then follows those instructions to create the image. For example, look at the image below :

      a ____________ b

A vector file for this image would contain instructions such as:

1. Draw a dot at point "a"
2. Draw a dot at point "b"
3. Connect the points together with a straight line of a certain thickness
4. Colour the line red

The size of the vector file does not change if the image needs to be larger - the same instructions will make the image as large as you like, and yet the line would always remain smooth and clear.

Vector image file size tends to be much smaller than the equivalent bitmap - as long as the image can be efficiently broken down into a set of instructions.