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Images have two properties that we're concerned with when dealing with
the World Wide Web (WWW) and both can be described by the term
"size". If we say an image is large in size, we could be referring to the image's dimensions (height and width),
such as the increasing dimensions from left to right of the images
shown below.
IMAGE SIZE
Or, we could be
referring to the file size (or the amount of disk space) the image
occupies, as shown by the file sizes below. File sizes are expressed
in megabytes (MB) or kilobytes (KB).
2KB 5KB 10KB FILE SIZE
Now that we've defined these terms, you should know that our main concern when creating images for the World Wide Web is file size. Why should we care about the file size of an image, you may ask? By keeping our images small in terms of file size, we help relieve an ever increasing load on our campus network and abroad. By optimizing your images, they can be transferred more quickly over the network and therefore will be painted on a viewer's computer screen in their browser more quickly. To some people there are few things more bothersome than browsing the World Wide Web and having to wait a minute or longer for an image on a web page to load up because of its sheer file size. Most of the time both of the terms image size and file size are directly proportional (e.g. large images usually mean large file sizes). But, it is all too common to see a small image size that takes up an inordinate amount of disk space. The image's dimension can play a big role in the file size, but it may not be feasible to make the image smaller in order to give your audience small file sizes. You may need a certain dimension so the person browsing your page can clearly see detail in your image. A picture of a map could be scaled down to reduce its file size, yet you might lose the detail needed for the viewer to make out tiny roads and streets. Therefore, we need to look at some possibilities other than reducing your image size when trying to be conservative with file size. The key term that I would like to stress is optimization. We want to optimize the images so that we have the highest quality image at the lowest cost in file size. On the following pages are some techniques that should help alleviate an ever increasing network bandwidth problem AND just as importantly - prevent frustrated users.
     
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