MIL-STD-2301 Computer Graphics Metafile Cgm Implementation Standard For The National Imagery Transmission Format StandardThis standard establishes the requirements necessary to implement Computer Graphics Metafiles CGM used for the representation of symbol graphics in the National Imagery Transmission Format Standard NITFS.

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MIL-STD-2301A

5.1.1.3.2  Edge Width Specification Mode element input.  The CGM implementation for NITFS shall provide the capability to input and interpret the Edge Width Specification Mode element using the following format.  Edge width is specified in "absolute mode," which indicates that the width is specified in source pixels. This command is used to support filled-area primitives.

TABLE XXV.  Edge Width Specification Mode input.

MSB                                                                                                                                                               LSB

15        14      13       12       11       10        9         8         7         6          5         4         3          2       1         0

2                                                            5                                                                  2                                 = 0x20A2

0                                                                                               = 0x0000

5.1.1.3.3  Line Width Specification Mode element input.  The CGM implementation for NITFS shall provide the capability to input and interpret the Line Width Specification Mode element using the following format.  Line width is specified in "absolute mode," which indicates that the width is specified in pixels.  This command is used to support the line primitive.

TABLE XXVI.  Line Width Specification Mode input.

MSB                                                                                                                                                               LSB

15        14      13       12       11       10        9         8         7         6          5         4         3          2       1         0

2                                                            3                                                                  2                                 = 0x2062

0                                                                                               = 0x0000

5.1.1.3.4  VDC Extent element input.  The CGM implementation for NITFS shall provide the capability to input and interpret the VDC Extent element using the following format.

TABLE XXVII.  VDC Extent input.

X1

Y1

X2

Y2

This element (illustrated on figures 2 and 3) defines the rectangular extent and orientation of the VDC space (the direction of the positive X and positive Y axes).  The extent and orientation of VDC space is indicated by giving the coordinates of lower left hand and upper right hand corners of the VDC extent.  The VDC extent space is a one-to-one map from the VDC extent to the source coordinates.  The VDC extent origin (0,0) is mapped onto the source at the row and column location given by the SLOC field in the Symbol Subheader for a given image.  The Symbol Subheader and the SLOC field are defined in the MIL-STD-2500B document.  Note that X1 and X2 cannot be equal, and Y1 and Y2 cannot be equal.  Note that the proper Character Orientation element must be present to ensure that CGM text is right side up for a given VDC Extent element.  The VDC extent defines the positive 90-degree angle to be the right angle from the positive X-axis to the positive Y-axis.

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