Corel DESIGNER Help | Computer Graphics Metafile (CGM)

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Computer Graphics Metafile (CGM) technical notes

Computer Graphics Metafile (CGM)

Computer Graphics Metafile (CGM) is an open, platform-independent metafile format used for storing and exchanging two-dimensional graphics. It supports RGB color. CGM files can contain both vector graphics and bitmaps, but they usually contain one graphic type or the other — rarely both.

Corel DESIGNER supports CGM Version 1, CGM Version 3, and the following CGM Version 4 profiles — ActiveCGM, WebCGM, S1000D, and ATA GREXCHANGE. The CGM Version 4 profiles are subsets of the CGM standard; each profile contains some CGM features. Files of these profiles allow associating of non-graphical data with graphical elements, and are often referred to as "intelligent graphics." Short descriptions of the supported Version 4 profiles follow.

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ACGM (ActiveCGM) — supports hyperlinking of both vector graphics and bitmaps, zooming, panning, hotspots, and database links. It is suitable for displaying 2D drawings on the Internet.

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WebCGM (versions 1.0, 2.0, and 2.1) — a binary file format that supports hyperlinks, document navigation, picture structuring and layers, as well as searching on WebCGM picture contents. It also supports Unicode and web fonts. The WebCGM profile is used widely in web electronic documents.

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S1000D (versions 2.3, 3.0, 4.0, 4.1, 4.2) — a standard that specifies requirements for creating graphics that are compliant with S1000D. S1000D is an international, SGML/XML-based standard for creating and managing technical publications. It was originally developed by the Aerospace and Defense Industries Association of Europe (ASD) for creating technical publications for military aircrafts. The standard has since been enhanced and is now supported by numerous industries for creating technical publications.

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ATA GREX (ATA GREXCHANGE) versions 2.4, 2.6, 2.8, 2.9, 2.10, 2.11, and 2.12— very similar to WebCGM in its rules for graphical elements. The ATA GREXCHANGE CGM profile is widely used in the civil aerospace industry.

Export options

When exporting to a CGM file, you can choose from various export options. The following list describes the controls in the CGM Export dialog box. Note that not all controls may be available for the version and profile you want to export to.

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Version — lets you choose CGM Version 1, 3, and 4

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Profile — available only for GGM Version 4. This list box lets you choose from many supported CGM Version 4 profiles.

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ICN — Information Control Number (ICN) is a document identifier in S1000D profiles (versions 2.3 to 4.2). The ICN box lets you add or edit a document identifier.

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GNBR — Graphic Number (GNBR) is a document identifier in ATA GREX profiles. The GNBR box lets you add or edit a document identifier.

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File encoding — lets you choose between Text and Binary file encoding provided the selected profile supports text encoding.

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Output precision (VDC) — VDC stands for Virtual Device Coordinate, which is the type of coordinate system used for positioning objects. If the coordinate system uses greater precision (more units) to describe the position of objects, the exported file will retain the original object position more accurately. Note that the output precision affects the file size. The High option (Real 32-bit) results in a bigger file size; the Low option (Integer 16-bit) keeps the file size smaller.

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Text controls

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Type — lets you choose the character encoding for text in the exported file: ISO 8859-1, UTF-8, or UTF-16. Both UTF-8 and UTF-16 can encode all characters defined by Unicode. ISO 8859 does not support characters that are not included in the Latin or Symbols character sets. To choose the encoding of unsupported characters, you can use the Character set mode and Fallback text encoding controls.

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Character set mode — The Strict mode replaces unsupported characters with the default character (typically, the question mark ?). The Relaxed mode preserves unsupported characters at the expense of profile violation by using the fallback encoding for ATA GREX.

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Fallback text encoding — The available options for encoding unsupported characters are UTF-8 and UTF-16.0.

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Color mode — controls how colors are exported, impacting the file size of the exported file. You can choose between the Indexed and Direct options. With the Direct option, the color values are stored with each shape in the document. With the Indexed option, the color values are defined once and then referenced in the shapes, typically resulting in a smaller file size. Some industry and company specifications impose a very strict file size limit on CGM files so it may be important to keep the CGM files small. The Color mode options are not available for ActiveCGM and CGM Version 1.

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Export layers — This check box lets you preserve layers in the exported file. If you don’t want to keep the layers, disable the check box.

To import a CGM file