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Hypermedia Basics

What is Hypermedia?

Hypermedia is a relatively new term created to describe the fusion of two other new technologies: multimedia and hypertext.

Multimedia refers to the capabilities of modern computers to provide information to a user in a number of different forms (sometimes called modalities) including images, graphics, video and audio information, in addition to the standard textual output of older computers.

Hypertext refers to the idea of linking different documents together using hyperlinks. A hyperlink often appears in a hypertext document as a piece of highlighted text. The text usually consists of a word or phrase that the user might require further information on. When the user activates the hyperlink, typically by clicking on it using a mouse, the user's view of the document is changed so as to show more information on the word or phrase concerned. This may mean that a different document is displayed on screen, perhaps positioned so that the relevant piece of text is at the top of the viewing screen; or alternatively, the original text might `unfold' to include some extra paragraphs providing the required information. The exact effect varies from implementation to implementation. Through the use of hyperlinks, many documents or parts of documents can be combined together to make a larger hypertext document. The hyperlinks make it very easy to follow cross-references between documents and so to look up related information. This often makes hypertext documents more suitable as reference manuals than conventional text manuals which must be accessed in serial fashion.

Hypermedia documents are simply hypertext documents with multimedia capabilities in addition. HIPR is a hypermedia document. Its basic structure is that of a hypertext document for ease of cross-referencing and information finding, but it also includes links to a library of images illustrating the effects of image processing operations, a multimedia capability. Of course, hypermedia documents in general can include many more types of multimedia information than simply images.

Hypermedia in Practice

In practice, in order to read a hypermedia document using a computer, a user needs two things. The first is the hypermedia document itself. This will be supplied in some machine-readable way (in a disk file typically) in a format that encodes the information content and hyperlink structure of the document. The second thing the user needs is some way of viewing the document in a human-readable way. This is usually done by a program called a hypermedia browser. The browser displays (or plays in the case of audio information) the information contained within the document to the user and also handles the processing of hyperlinks when required.

The hypermedia format used by HIPR is known as HTML (HyperText Markup Language), which is a language that has achieved great popularity recently since it is a cornerstone of the World Wide Web. The World Wide Web (or WWW) is a hypermedia system on a global scale, that links together documents and information all over the world via a collection of computer networks known as the Internet. Documents available via WWW are all encoded in HTML format and so a browser is necessary to display them on a computer screen. The most popular HTML browsers in use at the time of writing are Internet Explorer, available from Microsoft , and Netscape, available from Netscape Communications. HIPR is intended to work particularly well with Netscape, but it will work almost as well with any other graphical HTML browser. Note that only the HTML files are supplied with HIPR --- it is necessary to obtain and install Netscape or a similar viewer yourself separately. Fortunately, an increasingly large number of computer networks in universities and businesses have Netscape installed already, in order to access WWW, and the same setup can be used for viewing HIPR. Details of how to obtain Netscape if your system does not already have it are given in the Installation Guide.

Using HIPR with Netscape

The preferred HTML browser for use with HIPR is Netscape

Netscape is widely used to access the World Wide Web and is one of the better graphical HTML browsers available. It also has the advantage that it is available free from Netscape Communications and for a number of popular computer platforms. However, there are several other HTML browsers available and most of the graphically based ones should work just as well.

If you have managed to get this far, then you already know how to follow hyperlinks in text, and how to scroll the screen, but to summarize:

Hyperlinks appear as highlighted text. Their exact appearance varies according to how your browser is set up, but typically in Netscape they will appear as underlined text, possibly in a different color from normal text. To follow a hyperlink simply point at the link using the mouse and press the left mouse button once. The document at the other end of the hyperlink will then be displayed.

Some hyperlinks (known as `imagelinks'), cause images to be displayed when they are clicked on. In the hypermedia version of HIPR These image links appear as small pictures called thumbnails. Clicking on the image causes the full sized image to be displayed. In the hardcopy version of HIPR, imagelinks are simply printed as a filename in a typewriter font. The filename is the name of a file in the images sub-directory of HIPR that contains the full-sized image being referred to.

Try out this imagelink:


Note: On some Netscape setups, when the user clicks on an imagelink, the current document will be replaced in the Netscape window with the full-sized image. The disadvantage of this is that it makes it very difficult to read the text describing the image while viewing that image! One simple solution is to force Netscape to open a new full window when displaying the image (e.g. by clicking on the imagelink with the middle mouse button on UNIX systems). However, a full Netscape window is a rather cumbersome method of displaying images and so a better way is to instruct Netscape to display images using a specialized external viewer. Ask the person who installed HIPR on your system if it is possible to set this up. Details on how to do this are provided in the Installation Guide in the section on Using External Image Viewers.

If the displayed document is more than one screen long then a dark vertical bar with arrows at top and bottom will appear to the left or right of the the main document view. Clicking within this bar with the left or middle mouse button `scrolls' the document up or down so that you can see different parts of it. Experiment with this to get an idea of how it works.

Possible Problems

Monochrome vs Grayscale vs Color Displays

Since HIPR contains large numbers of images and graphics, many of which are in color, a color display is needed to show HIPR off at its best. However, HIPR can be displayed reasonably well with Netscape on grayscale or even monochrome (`black and white') screens. Most of the practical examples of image processing in HIPR use grayscale images for demonstration purposes, and so these will display perfectly well on grayscale screens. There may however be a few cases where it is difficult to differentiate between colors on a grayscale screen that are clearly distinct on a color screen. On monochrome screens, Netscape will use `dithering' to approximate grayscales. This means that some example images (particularly those containing lots of fine detail) will not show up very well.

Essential Hints and Tips

Other Useful Hints and Tips


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©2003 R. Fisher, S. Perkins, A. Walker and E. Wolfart.

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