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Web Graphics - Details

Reducing file-size

When you save a graphic for the Internet, it will probably be saved to either a GIF or JPG format [GIF vs JPG]. Your file will have a certain file size, depending on the dimensions and complexity of your image. Large file sizes take substantially longer to download, so any reduction in file size will result in enhanced delivery of your pages. There are software tools available to trim any extraneous information from your image files, so that the resulting download times can be reduced.

Some tips to speeding up your web pages with graphics:

• Use a software application to trim your file size. These are often called "optimisers" and 30 day demos are often available for download from the Internet. [Graphic Optimiser resources]

• Re-use the same graphics on more than one page. (Your browser often has a copy of recent files in its "cache").

• Specify the images width and height when inserting an image into your page. This allows the browser to plan layout more efficiently.

• Cheat when specifying your width and height. For example, instead of the usual <img src="pic.gif" height="24" width="32">, use <img src="pic.gif" height="36" width="48">. This technique may only be suitable for images which degrade only slightly from the resulting image distortion.

Tip: A large image can be divided into a number of adjacent images that assemble into the original image when the browser loads your page. The advantage of using this technique is that parts of the image start to be seen by the viewer almost immediately, whereas one large image gives the impression of being very slow to download and display. The downside of this technique is that your browser has to fetch a number of images rather than one.

This conflict between file size and download time will be resolved in time as users upgrade to ISDN, ADSL, Web-TV and other high-bandwidth media. In the meantime, however, choose your graphics carefully to meet the challenge of making as much impact as possible with small and economical graphics. Tastefully coordinated, these additions will add an important dimension to your web site, and elements like photographs are certainly essential to a school web site.