There are three CGMs (Computer Graphics Metafiles) in this collection. 

The contents of this CGM collection are: 



   ALLPRIMS.CGM  (a Clear Text metafile)

   CORVETTE.CGM  (a Binary metafile) 

   TECHDRAW.CGM  (a Binary metafile)



We have indicated the CGM encoding (there are three) with which each of

the files has been encoded.  Clear Text is human readable and can be

manipulated in normal text editors.  Binary is compact and efficient,

and the encoding most often used by implementors.  We have not included

a sample in the Character Encoding, as it is not much used in practice. 

Any CGM can be represented in any one of the three encodings with

equivalent graphical content, and there are tools available to convert

amongst the encodings. 



There are three other files associated with this collection.  



   ALLPRIMS.SUM

   CORVETTE.SUM

   TECHDRAW.SUM



These are summary reports produced by the MetaCheck (TM) product,

indicating at a summary level what each file contains and whether it is

a valid metafile (detailed disassemblies and trace reports are also

possible, but are too voluminous to be included here). 



A description of each file follows (a color rendition of each can be

found in the central color plates section of "The CGM Handbook",

L.Henderson and A.Mumford, Academic Press, 1993). 





CORVETTE.CGM

============



This file is a good example of typical CGM use in graphic arts

applications.  The picture is of a sleek and shiny Corvette sports car,

viewed headon and closeup, at sunset.  The foreground around the car and

receeding to the horizon is black.  Behind the car and above the horizon

is a sunset sky, shading from orange at the horizon, through pale green

and blue, to deep blue at the top.  Stars are beginning to appear in the

sky.  There is a row of palm trees on the horizon, in silouette but

catching the orange evening light.  The car is deep blue-black, with

parts of the hood and the windshield reflecting the colors of the

sunset.  The parking lights are on.  This file is a Binary-encoded CGM. 

It is drawn entirely using color filled polygons, rectangles, circles,

and ellipses, plus lines and text (and associated attributes). 

Extensive use is made of color.  The original source was a Genigraphics

graphics arts workstation, of the (former) Genigraphics Corp.  The

picture was produced circa 1988, and used in the CGM integration

demonstration (Integrate 88) at the NCGA 1988 Exposition. 





TECHDRAW.CGM

============



This file is a good example of the typical use of CGM in electronic

documents.  The Air Transport Association (ATA) -- commercial aircraft

manufacturers and the airlines themselves, as well as suppliers to the

industry -- has developed a program for delivery and use of technical

documents in revisable electronic form.  This is patterned after the

similar program in the US DoD, CALS (Computer-Aided Acquisition and

Logistic Support).  ATA documents comprise SGML for revisable text, and

CGM for revisable vector and raster graphics (TIFF has been included in

the past for purely raster graphics, but ATA is replacing its use by the

equally capable CGM:1992 Version 3 Tile Array element).  The picture is

a typical technical illustration from an aircraft maintenance manual,

including three views: the aircraft indicating assembly location; the

mounting area of a component panel; and, a complex illustration of the

subassembly itself (an electropneumatic drive unit for a flap).  The

picture is a black-and-white line drawing, using only line and text

elements (and a few associated attributes).  This file is a

Binary-encoded CGM.  The source is a requirements document for standard

graphics exchange, produced by the ATA Graphics Working Group, circa

1991. 





ALLPRIMS.CGM

============



This CGM file is interesting for two reasons: it contains at least one

instance of 18 of the 19 graphical primitives of Version 1 metafiles of

CGM:1992 -- Polyline, Polymarker, Text, Polygon Set, Cell Array,

Elliptical Arc Close, etc -- plus a good sampling of the 35 attribute

elements; and, it is in the Clear Text encoding so you can read the

contents and see what CGM structure and elements look like.  The one

omitted primitive is GDP (Generalized Drawing Primitive, which is a more

or less private extension element).  The picture is composed of a grid

of 18 large cells -- 3 rows of 6 cells each.  Each cell contains a

sample of one of the Version 1 graphical primitives, along with a label

identifying the primitive.  Color is used, different interior styles for

filled-area elements are used, wide and narrow lines are used, etc.  At

the bottom, under and contiguous to the grid of cells, is a low wide

block containing samples of the 5 standard CGM line types, and to the

right is a documentation block with the metafile "pedigree".  This file

was originally produced by the CTN, the CALS Test Network (CALS is the

DoD Computer-Aided Acquisition and Logistics Support program, whose

standards-based revisable electronic document program calls for CGM as

the preferred format for delivery of revisable electronic documents). 

CTN's role with CGM is to identify and test the standards concepts

themselves, perform informal interoperability events, etc.  CTN does not

do validation or certification testing for CGM and CGM implementations. 

NIST (the National Institute of Standards and Technology) is now

performing this role.



ftp://ftp.kfunigraz.ac.at/pub/unix/tools/graphics_file_formats/formats/CGM/IMAGE/