Computer Graphics Metafiles (GKSM and CGM)

A graphics metafile is a computer file containing a set of data records describing a graphical image. It may be used for

1. Transporting graphical information between different types of computers.
2. Transporting graphical information from one site to another. (by magnetic tape for example)
3. Transporting graphical information from one application to another.
4. Device spooling, e.g. for a plotter.

As yet there is no official ISO standard for writing a GKS Metafile (GKSM). However, the ISO GKS Functional Description assumes the existence of one and, in Appendix E of the document, a metafile format is described and its use is recommended. A GKS metafile created using this format is known as an Appendix E metafile. Unfortunately, not all implementations follow the Appendix E format, and so GKSM metafiles created by different GKS packages may be incompatible. In fact, even different examples of Appendix E metafiles may be incompatible due to variations in the file record structures, etc.

The Computer Graphics Metafile (CGM) has been produced by a separate standards group within ISO and, when implementations become available, it will be an alternative to the Appendix E metafile for the storage and transmission of complete pictures. One should note that because CGM is an independent standard compatible with GKS, it is expected to become adopted as the picture interchange format used between all graphics standards.