Name of the image format for the bitmap that is provided with a <glyph-data> element. This element is used to define a private use character when the <private-char> contains a bitmap.
If a plain bitmap is included inline, the value of this attribute should be “PBM”, indicating that the plain text bitmap will be a human-readable matrix of zeros and ones.
Used on Element: <glyph-data>
|A word||A word naming the format of the bitmap. The word may not contain any spaces, and the characters of the word are limited to letters, numbers, and these special characters: period, hyphen, underscore, and colon.|
|Restriction||@format is an optional attribute; there is no default.|
... <private-char name="NORTHWEST SOUTHEAST ARROW" description="Arrow, normal weight, single line, two-headed, Northwest to Southeast"> <glyph-data id="NWSEArr" format="PBM" resolution="300" x-size="34" y-size="34"> ...</glyph-data></private-char> ...