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

5.1.1.4  Attribute elements.  Attribute elements are used to describe the appearance of the Graphical

Primitive elements.

5.1.1.4.1  Text Color element input.  The CGM implementation for NITFS shall provide the capability to input and interpret the Text Color element using the following format.  The Text Color element is used to support the text primitives.  Red, Green, and Blue (RGB) values are specified using a single byte, and the last byte of the command shall be a null byte.

TABLE XXVIII.  Text Color input.

5                                                           14                                                                 3                                 = 0x51C3

RED                                                                               GREEN BLUE                                                                                    0

5.1.1.4.2  Character Height element input.  The CGM implementation for NITFS shall provide the capability to input and interpret the Character Height element using the following format.  Variable character heights, as measured from baseline to capline, shall be supported.  The font, if given, is specified by the Font List and Text Font Index elements.

TABLE XXIX.  Character Height input.

CHARACTER_HEIGHT

5.1.1.4.3  Text Font Index element input.  The CGM implementation for NITFS shall provide the capability to input and interpret 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 XXX.  Text Font Index input.

TEXT_FONT_INDEX

5.1.1.4.4  Character Orientation element input.  The CGM implementation for NITFS shall provide the capability to input and interpret 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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