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

5.1.2.4  Attribute elements.  The Attribute elements are used to describe the appearance of the Graphical Primitive elements.  Full color may be specified for the Elements dealing with color.  Color items for receiving systems unable to support full color must be mapped to colors they are able to support.

5.1.2.4.1  Text Color element output.  The CGM implementation for NITFS shall provide the capability to generate and output the Text Color element using the following format.  The Text Color element is used to support the text primitives.  RGB values are each specified using a single byte, and the last byte of the command shall be a null byte.

TABLE LXXXV.  Text Color output.

5                                                           14                                                                 3                                 = 0x51C3

RED                                                                               GREEN BLUE                                                                                    0

5.1.2.4.2  Character Height element output.  The CGM implementation for NITFS shall provide the capability to generate and output the Character Height element using the following format.  As measured from baseline to capline, variable character heights shall be supported.  If given, the font is specified by the Font List and Text Font Index elements.

TABLE LXXXVI.  Character Height output.

CHARACTER_HEIGHT

5.1.2.4.3  Text Font Index element output.  The CGM implementation for NITFS shall provide the capability to generate and output the Text Font Index element using the following format.  The Text_Font_Index parameter is the index into the Font List array created from the Font List element for selection of a particular font.

TABLE LXXXVII.  Text Font Index output.

TEXT_FONT_INDEX

5.1.2.4.4  Character Orientation element output.  The CGM implementation for NITFS shall provide the capability to generate and output the Character Orientation element using the following format.  This command defines the orientation and skew of the character body in subsequent text elements.  Since the VDC Extent element is used to establish the direction of the positive X and positive Y axis, the character orientation must be present to ensure that text characters are always upright from left to right when the VDC Extent element defines Y increasing down or X increasing left.  The following four cases apply to the Character Orientation element for each possible VDC extent orientation.

a.  VDC Extent element with X increasing right and Y increasing up (X1<X2 and Y1<Y2).

Character Orientation element not required or Y=1 and X=1 when Character Orientation present. b.  VDC Extent element with X increasing right and Y increasing down (X1<X2 and      Y1>Y2).

Character Orientation element required with Y=-1 and X=1.

c.  VDC Extent element with X increasing left and Y increasing up (X1>X2 and Y1<Y2).

Character Orientation element required with Y=1 and X=-1.

d.  VDC Extent element with X increasing left and Y increasing down (X1>X2 and Y1>Y2).

Character Orientation element required with Y=-1 and X=-1.

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