AGOCG logo
Graphics Multimedia VR Visualisation Contents
Training Reports Workshops Briefings Index

WEB Browser for CGMs

While the World-Wide Web has grown at a prodigious rate, one recurring criticism has been the poor performance when graphics are included in pages. A contributory factor to this is that all graphics have been stored, and therefore transmitted, as image files, which are inefficient for graphics that were originally line drawings such as most CAD output, maps, organizational diagrams and the like. With support from AGOCG RAL-CGM, one of the more widely used CGM interpreters, has now been extended so that it can act as a Web browser in Mosaic and Netscape, adding geometric graphics to the Web's capabilities.

The Computer Graphics Metafile (International Standard 8632) is the standard format for the storage and exchange of 2D graphics, and is widely supported by packages that generate 2D graphics. CGM provides a compact form for 2D graphics, reducing storage costs and transmission times; it supports a wide range of functions and is an integral component of CALS, thus ensuring it has US government support.

Work has been in hand, through the Graphics Coordinator (Anne Mumford) and Alan Francis, to register CGM as a MIME data type; this will allow CGMs to be used in applications (such as e-mail) that allow MIME extensions. Rutherford Appleton Laboratory (RAL) has raised the subject of registering CGM as an approved file type for the Web with W3C - the World-Wide Web Coordination group - and this is proceeding.

RAL-CGM, developed at the RAL, is a comprehensive interpreter for all forms of Computer Graphics Metafile (IS 8632). It can interpret all the standard encodings, producing output on-screen (Windows, X-Windows, various other devices) or in a file (all CGM encodings and PostScript).

RAL-CGM has now been extended so that it can act as an external viewer under Mosaic and Netscape Web browsers and the code is available, without charge, from:

RAL are continuing to develop RAL-CGM, both as a stand-alone system and as a Web viewer, towards the more recent version of the CGM document which adds many new elements and enhanced capability.

Chris Osland