Computer Graphic Metafile

Long name Computer Graphic Metafile
Short name CGM
File extension(s) .cgm

The Computer Graphic Metafile (CGM v1.0) implementation for NITFS (The National Imagery Transmission Format Standards) is a subset of the Federal Information Processing Standard FIPS PUB 128 and complies with the specifications established in FIPS PUB 128. The GDB library supports CGM as symbol assignment file for importing and viewing; GDB can also open CGM files as 'general' file format.

The CGM implementation for NITFS supports interpretation. The descriptions below are grouped by element class.

The following shows the basic content of the CGM file format:

a. Metafile Delimiter Elements

           BEGIN METAFILE
           BEGIN PICTURE
           BEGIN PICTURE BODY
           END PICTURE
           END METAFILE

b. Metafile Descriptor Elements

           METAFILE VERSION (version = 1)
           METAFILE ELEMENT LIST
           METAFILE DESCRIPTION
           FONT LIST

c. Metafile Picture Descriptor Elements

           COLOR SELECTION MODE (1 = direct)
           EDGE WIDTH SPECIFICATION MODE (0 = absolute)
           LINE WIDTH SPECIFICATION MODE(0 = absolute)
           VDC EXTENT

d. Metafile Graphical Primitives with Associated Attributes

           Text Primitive Element with Attributes

               TEXT COLOR
               CHARACTER HEIGHT
               TEXT FONT INDEX
               CHARACTER ORIENTATION
               TEXT

           Filled Area Primitive Elements with Attributes

               FILL COLOR
               INTERIOR STYLE (1= solid or 4 = empty)
               EDGE VISIBILITY (1 = on)
               EDGE WIDTH
               EDGE TYPE (1=solid or 2=dashed)
               EDGE COLOR
               POLYGON

               ELLIPSE
               ELLIPTICAL ARC CLOSE
               RECTANGLE
               CIRCLE
               CIRCULAR ARC CENTER CLOSE

           Line Primitive Elements with Attributes

               LINE WIDTH
               LINE TYPE (1=solid or 2=dashed)
               LINE COLOR

               POLYLINE
               ELLIPTICAL ARC
               CIRCULAR ARC CENTER

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