Computer Graphics Metafile
Encyclopedia
Computer Graphics Metafile (CGM) is a free and open
international standard
file format for 2D vector graphics
, raster graphics
, and text
, and is defined by ISO
/IEC
8632.
elements can be specified in a textual source file that can be compiled into a binary file
or one of two text representations. CGM provides a means of graphics data interchange for computer representation of 2D graphical information independent from any particular application, system, platform, or device.
As a metafile
, i.e. a file containing information that describes or specifies another file, the CGM format has numerous elements to provide functions and to represent entities, so that a wide range of graphical information and geometric primitives can be accommodated. Rather than establish an explicit graphics file format, CGM contains the instructions and data for reconstructing graphical components to render an image using an object-oriented approach.
Although CGM is not widely supported for web pages and has been supplanted by other formats in the graphic arts, it is still prevalent in engineering, aviation, and other technical applications.
The initial CGM implementation was effectively a streamed representation of a sequence of Graphical Kernel System
primitive operations. It has been adopted to some extent in the areas of technical illustration
and professional design
, but has largely been superseded by formats such as SVG
and DXF
.
The World Wide Web Consortium
has developed WebCGM, a profile of CGM intended for the use of CGM on the Web.
Open standard
An open standard is a standard that is publicly available and has various rights to use associated with it, and may also have various properties of how it was designed . There is no single definition and interpretations vary with usage....
international standard
International standard
International standards are standards developed by international standards organizations. International standards are available for consideration and use, worldwide...
file format for 2D vector graphics
Vector graphics
Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygon, which are all based on mathematical expressions, to represent images in computer graphics...
, raster graphics
Raster graphics
In computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...
, and text
Character (computing)
In computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written form of a natural language....
, and is defined by ISO
International Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
/IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
8632.
Overview
All graphicalComputer graphics
Computer graphics are graphics created using computers and, more generally, the representation and manipulation of image data by a computer with help from specialized software and hardware....
elements can be specified in a textual source file that can be compiled into a binary file
Binary file
A binary file is a computer file which may contain any type of data, encoded in binary form for computer storage and processing purposes; for example, computer document files containing formatted text...
or one of two text representations. CGM provides a means of graphics data interchange for computer representation of 2D graphical information independent from any particular application, system, platform, or device.
As a metafile
Metafile
Metafile is a generic term for a file format that can store multiple types of data. This commonly includes graphics file formats. These graphics files can contain raster, vector, and type data...
, i.e. a file containing information that describes or specifies another file, the CGM format has numerous elements to provide functions and to represent entities, so that a wide range of graphical information and geometric primitives can be accommodated. Rather than establish an explicit graphics file format, CGM contains the instructions and data for reconstructing graphical components to render an image using an object-oriented approach.
Although CGM is not widely supported for web pages and has been supplanted by other formats in the graphic arts, it is still prevalent in engineering, aviation, and other technical applications.
The initial CGM implementation was effectively a streamed representation of a sequence of Graphical Kernel System
Graphical Kernel System
The Graphical Kernel System was the first ISO standard for low-level computer graphics, introduced in 1977. GKS provides a set of drawing features for two-dimensional vector graphics suitable for charting and similar duties...
primitive operations. It has been adopted to some extent in the areas of technical illustration
Engineering drawing
An engineering drawing, a type of technical drawing, is used to fully and clearly define requirements for engineered items.Engineering drawing produces engineering drawings . More than just the drawing of pictures, it is also a language—a graphical language that communicates ideas and information...
and professional design
Industrial design
Industrial design is the use of a combination of applied art and applied science to improve the aesthetics, ergonomics, and usability of a product, but it may also be used to improve the product's marketability and production...
, but has largely been superseded by formats such as SVG
Scalable Vector Graphics
Scalable Vector Graphics is a family of specifications of an XML-based file format for describing two-dimensional vector graphics, both static and dynamic . The SVG specification is an open standard that has been under development by the World Wide Web Consortium since 1999.SVG images and their...
and DXF
AutoCAD DXF
AutoCAD DXF is a CAD data file format developed by Autodesk for enabling data interoperability between AutoCAD and other programs....
.
The World Wide Web Consortium
World Wide Web Consortium
The World Wide Web Consortium is the main international standards organization for the World Wide Web .Founded and headed by Tim Berners-Lee, the consortium is made up of member organizations which maintain full-time staff for the purpose of working together in the development of standards for the...
has developed WebCGM, a profile of CGM intended for the use of CGM on the Web.
History
- 1986 – ANSI X3 122-1986 (ANSIAmerican National Standards InstituteThe American National Standards Institute is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international...
X3 committee) - 1987 – ISO 8632-1987 (ISOInternational Organization for StandardizationThe International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
) - 1991 – ANSI/ISO 8632-1987 (ANSI and ISO)
- 1992 – ISO 8632:1992, a.k.a CGM:1992 (ISO)
- 1999 – ISO/IEC 8632:1999, 2nd Edition (ISO/IEC JTC1/SC24ISO/IEC JTC1ISO/IEC JTC 1 is Joint Technical Committee 1 of the International Organization for Standardization and the International Electrotechnical Commission . It deals with all matters of information technology....
) - December 17, 2001 – WebCGM (W3CWorld Wide Web ConsortiumThe World Wide Web Consortium is the main international standards organization for the World Wide Web .Founded and headed by Tim Berners-Lee, the consortium is made up of member organizations which maintain full-time staff for the purpose of working together in the development of standards for the...
) - January 30, 2007 – WebCGM 2.0 (W3C)
- March 1, 2010 – WebCGM 2.1 (W3C Recommendation)
Further reading
- Arnold, D.B. and P.R. Bono, CGM and CGI: Metafile and Interface Standards for Computer Graphics, Springer-Verlag, New York, NY, 1988.
- Henderson, L.R., and Gebhardt, "CGM: SGML for Graphics," The Gilbane Report, Fall 1994.
- Henderson, L.R., and A.M. Mumford, The CGM Handbook, Academic Press, San Diego, CA, 1993.
- Bono, P.R., J.L. Encarnacao, L.M. Encarnacao, and W.R. Herzner, PC Graphics With GKS, Prentice-Hall, Englewood Cliffs, NJ, 1990.
General
- Overview of CGM Standards
- CGM File Format Summary
- WebCGM at a glance
- Technology Reports: WebCGM
- Use of CGM as a Scalable Graphics Format
Standards
- WebCGM 1.0, W3C Recommendation, 17 December 2001
- WebCGM 2.0, W3C Recommendation, 30 January 2007
- WebCGM 2.1, W3C Recommendation, 1 March 2010
- ISO/IEC 8632-1:1999/Cor.2:2007 Part 1: Functional specification
- ISO/IEC 8632-3:1999 Part 3: Binary encoding
- ISO/IEC 8632-4:1999 Part 4: Clear text encoding