Session 1: Types of image
There are two main types of image, and these are vector and bitmap and each of these
are available in many different formats. However, web page standards currently only support
three formats of bitmap images, and no vector images. Vector images and other formats
of bitmap image need the use of a 'plugin' or other form of operating system support
for them to be displayed with a web page.
Vector images
A vector image is one which is specified using outlines and fill patterns to make
up the image. This means that each component of the image is individually accessible,
and can be edited with appropriate software. The following two images show a bug
and the same bug exploded into its component parts.
Another advantage of vector images is that they scale well. If you zoom in on an
image it will continue to have smooth edges, with no deterioration in quality. The
images below show this effect:
Couple this with the inherent small size of the image files and you have an effective
format. However, vector graphics formats are more suitable for drawn images and
cannot be used for photographs. You have to bear in mind that not all users will
be able to see the image unless they have appropriate software installed.
Common examples of vector image formats are: Windows Metafile (WMF) and Scalable
Vector Graphic (SVG). WMF files are supported natively by Windows based clients,
but as an open file format it is supported (maybe using a plugin) on other platforms.
SVG files needs a plugin from Adobe, even though the standard is ratified by W3C,
as XHTML browsers are not compelled to support it.