HP PCL 5 Comparison Manual page 87

In the MS-Mincho and MS-Gothic fonts provided in the HP
LaserJet 4PJ, font metric calculation is somewhat easier
than for the Latin-based fonts. Width calculations are
easier because all characters of these fonts conform to one
of two different character widths at a particular point size.
The characters are either considered full-width or half-
width. One-byte characters are always half-width and
two-byte characters are always full-width.
Full-width characters occupy the entire EM width at a
particular point size. Half-width characters occupy half of
an EM width. The following equations show how to
calculate the EM width and character widths for a
full-width and a half-width character.
ppem = round (DeviceResolution * PointSize/72)
FullWidthDeltaX = round (ppem * PCLUnits/ DeviceResolution)
HalfWidthDeltaX=round ((ppem/2) * PCLUnits/DeviceResolution)
where:
ppem = EM width in pixels
DeviceResolution = current device resolution in dots per inch
(600 or 300dpi)
PointSize = point size requested
FullWidthDeltaX = character width of full-width character in PCL
Units
HalfWidthDeltaX = character width of half-width character in PCL
Units
PCLUnits = PCL Units
The PCL Unit of measure is explained in more detail in the
PCL 5 Technical Reference Manual. The default PCL Unit
size is 1/300th of an inch, but the Unit of Measure command
can be used to set the PCL Unit size to other values.
Note that HalfWidthDeltaX may not be exactly half of
FullWidthDeltaX because of rounding. For example, if
FullWidthDeltaX = round(99.0) = 99, then the
corresponding HalfWidthDeltaX = round(99.0/2) =
round(49.5) = 50.
Printer-Specific Differences 2-51