Font bitmaps

Font bitmap files require two characteristics in addition to the above to be uniquely identifiable: (1) the type of device (i.e., mode) for which the font was created; (2) the resolution of the bitmap.

Following common practice, the TDS segregates fonts with different device types into separate directories. See `modes.mf' in Appendix section Related references for recommended mode names.

Some printers operate at more than one resolution (e.g., at 300dpi and 600dpi), but each such resolution will necessarily have a different mode name. Nothing further is needed, since implicit in the TeX system is the assumption of a single target resolution.

Two naming strategies are commonly used to identify the resolution of bitmap font files. On systems that allow long filenames (and in the original METAFONT program itself), the resolution is included in the filename (e.g., `cmr10.300pk'). On systems which do not support long filenames, fonts are generally segregated into directories by resolution (e.g., `dpi300/cmr10.pk').

Because the TDS cannot require long filenames, we must use the latter scheme for naming fonts. So we have two more subdirectory levels under `pk' and `gf':

texmf/fonts/pk/mode/supplier/typeface/dpinnn/
texmf/fonts/gf/mode/supplier/typeface/dpinnn/

• `mode' is a name which identifies the device type (examples: `cx', `ljfour', `modeless'). Usually, this is the name of the METAFONT mode used to build the `PK' file. For fonts rendered as bitmaps by a program that does not distinguish between different output devices, the `mode' name shall be simply `modeless'. The `mode' level shall not be omitted, even if only a single mode happens to be in use.
• `dpinnn' specifies the resolution of the font (examples: `dpi300', `dpi329'). `dpi' stands for dots per inch, i.e., pixels per inch. We recognize that pixels per millimeter is used in many parts of the world, but dpi is too traditional in the TeX world to consider changing now. The integer `nnn' is to be calculated as if using METAFONT arithmetic and then rounded; i.e., it is the integer METAFONT uses in its output `gf' filename. We recognize small differences in the resolution are a common cause of frustration among users, however, and recommend implementors follow the level 0 DVI driver standard (see Appendix section Related references) in bitmap font searches by allowing a fuzz of +-0.2% (with a minimum of 1) in the `dpi'.

Implementations may provide extensions to the basic naming scheme, such as long filenames (as in the original METAFONT) and font library files (as in emTeX's `.fli' files), provided that the basic scheme is also supported.

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