School of GeoSciences

School of GeoSciences

Images for the School Web Site

Some things to know about images in general:

  • Copyright: The copyright of any image displayed on the website must be owned by the university or have been approved by the copyright holder for use (if a member of staff has taken the photo and put it on the website him/herself, or given it to a webeditor so to do, that is taken as tacit acknowledgement of copyright clearance). As well as images owned by the university there are a number of sources of 'copyright free' images that can be used such as some US government sources.

  • Formats: There are a wide range of image formats in use in Information Technology. Only 3 formats are displayed in-line in web browsers: jpg, gif and png.

  • JPEG (jpg): This format is suitable for photographs. The original image is compressed using a lossy method that reduces the file size by up to 90%. Because the method is lossy, JPEG images should not be repeatedly reprocessed.

  • Graphics Interchange Format (gif): This format is suitable for line art (i.e. any form of graphic consisting largely of areas of uniform colour, such as Logos, Cartoons and Charts. It is the subject of patent disputs and should be avoided. The format is produced by lossless compression of an original image restricted to 256 colours. It is NOT suitable for photographs.

  • Portable Network Graphics (png): This is a replacement for gif avoiding the patent dispute issue and offering numerous additional features. It should be used for line-art in preference to gif.

  • Image Size: Images for the web are measured in pixels (colour dots) in width and height. Whatever the original size, reduce the image to a size suitable for web display before uploading. Images should not be more than 600 pixels wide without good reason. Half this size is usually preferable. If the image is big users may have to scroll the screen horizontally, and they may resent waiting for it to arrive.

  • Network bandwidth: Image files can be very big! The JPEG images produced by a digital camera can be up to 2Mb. A 56K modem might take 5 minutes to fetch such an image. Even with a broadband connection the delay whilst the image is fetched will be noticeable. So, keep images as small as they need to be. If it is necessary to provide full size images, provide a thumbnail index and state the file-size of the full-size image.

Graphics Software

There are a large number of applications available for producing graphic images for the web. Some are free, some are expensive, some are Shareware that let you try before you buy. The selection of a suitable package is beyond the scope of this documentation.

First: find out what is installed on your network.