Name

vfontas — a bitmap font file transformation utility

Syntax

vfontas commands...

Commands

-blankfnt

-canvas xsize ysize

-clearmap

-crop xpos ypos width height

-fliph

-flipv

-invert

-lge

-lgeu

-lgeuf

-loadbdf ff.bdf

-loadclt directory/

-loadfnt mu.fnt

-loadhex unicode.hex

-loadmap cp437AB.uni

-loadpsf ter-v32b.psfu

-move shiftx shifty

-savebdf out.bdf

-saveclt outdir/

-savefnt x.fnt

-saven1 new.sfd

-saven2 new.sfd

-savepbm outdir/

-savepsf new.psfu

-savesfd new.sfd

-setbold

-setname name

-setprop key value

-upscale xscale yscale

-xcpi ega437.cpi outdir/

-xlat xoffset yoffset

Description

vfontas (originally "VGA font file assembler") can read/write bitmap fonts from/to a number of formats and transform the glyphs in various ways. vfontas is able to generate a vector format.

vfontas does not have a direct integration of or with FontForge, but thanks to the BDF read/write support on both sides, fonts in formats like FNT and PSF can be made available to FontForge by vfontas, and, conversely, fonts in formats like FON and TTF can be made available to vfontas by FF.

With its own CLT format, vfontas makes glyphs in a textgraphical format to facilitate editing with plain-text screen editors such as vi, nano, etc.

Aspect ratio

CRT screens of the time commonly had an aspect ratio of 4:3, and whatever resolution was shown would be squeezed into that frame, potentially making the pixels non-square. This means that bitmap fonts of the time will need a corrective factor for modern display hardware to be reproduced faithfully. This correction can happen either during conversion (vfontas has no support for this at present), or at the time of rendering. The font can either be stretched in the vertical direction or compressed in the horizontal by using the reciprocal.

Text res	Char size	Resolution	VStretch
80x25	9x14	720x350	54/35 = 1.54
40x25	8x8	320x200	6/5 = 1.2
80x25	8x8	640x200	12/5 = 2.4
80x25	8x14	640x350	48/35 = 1.37
80x43	8x8	640x350	48/35 = 1.37
80x25	9x16	720x400	27/20 = 1.35
80x30	8x16	640x480	1.0
80x50	9x8	720x400	27/20 = 1.35
		x*y	xy/34

Commands

blankfnt

Initializes the memory buffer with 256 empty 8x16 glyphs. The primary purpose for this is with saveclt to get blank glyph files for hand-editing. For a differently-sized canvas, combine with -crop or -canvas.

canvas

Enlarges the glyph box to the specified size. (It never shrinks it.)

clearmap

Discards the in-memory glyph index <-> Unicode mapping table.

crop

Removes an outer area from the glyph images, shrinking the image in the process.

fliph, flipv

Mirrors/flips glyphs.

lge

Applies a "Line Graphics Enable" transformation on glyphs. It copies the pixels in the second rightmost column to the rightmost column, and does this for glyph indices 0xC0 to 0xDF. In other words, the usefulness of the -lge command is more or less limited to DOS fonts which have graphic characters in exactly those indices.

lgeu

Applies LGE on the graphic glyphs that are in cp437 and other DOS codepages. It does this for unicode codepoints rather than glyph indices. This is suitable for all kinds of font formats, but do make sure a Unicode table is present. (BDF and PSF come with a table, .fnt does not, so use -loadmap before -lgeu).

lgeuf

Applies LGE on all glyphs from U+2500 thru U+25FF (Unicode "box drawing" and "box elements" classes), with special handling for the shades at U+2591 thru U+2593. This is provided as an alternative to the "true DOS look" that lge/lgeu would make.

loadbdf

Reads a BDF (Adobe Glyph Bitmap Distribution Format) font file.

loadclt

Reads a directory full of CLT files containing glyphs. CLT is a textgraphical format to facilitate visual editing with a text console editor.

loadfnt

Reads a headerless bitmap font file, as typically used for CGA/EGA/VGA/MDA hardware, from the specified file into memory. 8x8x256 (width/height/glyphs), 8x12x256, 8x14x256, 8x16x256 and 8x16x512 are supported.

loadfnth

Reads a headerless bitmap font file, using the specified height N and width 8. The number of characters is then autoderived from the filesize.

loadhex

Reads a Unifont .hex encoded file.

loadmap

Reads a glyphindex <-> Unicode codepoint mapping table from the given file into memory. The format follows the maps from /usr/share/kbd/unimaps, that is, "0x00 U+0000" at its simplest. Multiple U+ codepoints can be specified in a line. -loadmap does not clear the mapping table, which makes it possible to cumulate mappings from multiple files.

loadpsf

Reads a PC Screen Font PSF 2 version 0. If the psf file comes with a mapping table, the current in-memory table will be discarded and replaced with the one from the PSF.

move

Shift all glyphs by the given x/y offsets within their existing glyph box (possibly truncating them).

savebdf

Saves the font to a Glyph Bitmap Distribution Format file (BDF). This type of file can be processed further by other tools such as bdftopcf(1) or fontforge(1) to, for example, turn them into Portable Compiled Format (PCF) or TrueType/OpenType (TTF/OTF) files. (See the "Examples" section.)

saveclt

Saves the current in-memory glyphs as multiple CLT files to the given directory. CLT is a textgraphical format to facilitate visual editing with a text console editor.

savefnt

Saves the current in-memory glyphs to the given file, using the headerless format.

savemap

Saves the current in-memory Unicode mapping table to the given file.

saven1

N1 was an experiment to try and model the "diagonalization idea" (cf. -saven2) by analyzing the original glyph bitmap. Its defining characteristic is a lookaround window of 3x3 pixels, whose contents are mapped to a set of triangles. N1 has some drawbacks over the newer N2:

N1 adds diagonals on single-pixel protrusions (e.g. the left end of the horizontal bar in an 'f' in certain fonts). This is definitely not fixable with a 3x3 window and would require using 5x5.
N1 adds triangles between pixels that do not necessarily belong together, such as in spirals like U+0040 or jampacked glyphs like U+20A7. N2 operates on edges and knows their direction, and avoids making connections to "pixel islands" at certain angles.

saven2

Similar to -savesfd, this produces an SFD file, but uses an alternate vectorizer (aptly named "N2"), which smoothens the jagged edges of a bitmap font.

The N2 vectorizer is able to recognize the "stair" pattern of pixels and transform these sections to 45-degree angles. This diagonalization was originally employed by Arto Hatanpää (possibly in a long session of manual work) for the "Nouveau IBM" and "Nouveau IBM Stretch" vector font versions of the IBM VGA 9x16 ROM font.

The defining characteristic of N2 is that it analyzes glyph edges (similar to those produced by -savesfd) using a lookaround window of 7 edge segments, which is used to work on areas of effectively 5x5 pixels. When a 90/270 corner is found, it will be transformed by adding diagonal edges.

In comparison to other scalers,

xBRZ erroneously round the ends of strokes (e.g. the '-' dash), N1/N2 does not.
While xBRZ is a bitmap-to-bitmap procedure (also limited to 6x magnification as of writing), N1/N2 converts to vector.
Autotrace/Potrace just is not targeted for low resolution sources (as 8x16 bitmap fonts are). Either it will convert the bitmap 1:1 with jagged edges, or turn it into three or so beziers, which is not nearly enough for '&'.
N1/N2 is only specified for monochrome input.

savepsf

Saves the current in-memory glyphs as a PC Screen Font PSF2.0 file, which can then be loaded into a Linux text console with setfont(1). The in-memory Unicode mapping table is added to the PSF.

savesfd

Saves the font to a Spline Font Database file (SFD). This type of file can be processed further by fontforge(1). A fairly trivial vectorizer is used that maps each pixels to a square and then collapses shared edges between those to reduce the number of polygons fontforge has to process.

setbold

For BDF/SFD output: Declare the font as being bold.

setname

Sets a name for the font, which gets emitted for BDF/SFD output. (The other file formats have no metadata field for a name, so the filename is all you get.)

setprop

Sets a specific property for SFD fonts (also partly used by BDF).

upscale

Performs a linear upscale by an integral factor for all glyphs.

xcpi

Extracts a multi-font .cpi file (as was typically used on DOS) as separate .fnt files into the specified directory. This operation does not touch the in-memory glyph buffers or Unicode mapping table.

xlat

Moves all glyphs around within their canvases by the specified amount. vfontas's coordinate system has (0,0) in the upper left corner, with positive x going to the right, and positive y going down.

Known limits

The Linux kernel accepts console font glyphs of at most 32x32 in size.

The Consoleet bitmap format

The Consoleet text bitmap format is very similar to PBM itself. Instead of "P1" as in PBM, a CLT file begins with "PCLT" on the first line. In the second line, width and height of the bitmap in pixels is given. What follow is the bitmap data: Each "off" pixel is represented by the 2-character string ".." Each "on" pixel is represented by the 2-character "##". Each row of pixels is terminated by a newline, like in PBM.

	PCLT
	9 7
	..................
	....##....##..##..
	..##..##..##..##..
	..##..##..####....
	..##..##..##..##..
	....##....##..##..
	..................

Examples

Decompose a classic file into editable pictograph text files (with the help of a Unicode map):

mkdir mu; vfontas -loadfnt /usr/share/kbd/consolefonts/mu.fnt -loadmap
/usr/share/kbd/unimaps/cp437.uni -saveclt mu/

To convert a .fnt and scale it up to make it comfortably usable with a FullHD resolution Linux fbconsole:

vfontas -loadfnt mu.fnt -loadmap cp437.uni -canvas 9 16 -lge -upscale 2 2
-savepsf mu.psf

To convert a .fnt to TrueType/OpenType/WOFF (the Fontforge part is unfortunately manual):

vfontas -loadfnt mux.fnt -loadmap cp437AB.uni -canvas 9 16 -lge -savesfd
mux.sfd # && fontforge mux.sfd

To convert a .fnt for use under X11 and XTerm (generates sizes 12, 24 and 36, @96dpi):

for i in 1 2 3; do vfontas -loadfnt mux.fnt -loadmap cp437AB.uni -canvas 9
16 -lge -upscale $i $i -setname Mux -savebdf | bdftopcf | gzip
>~/.fonts/mux$i.pcf.gz; done; xterm -fa "misc Mux:size=24"

Comparison to earlier vfontas (2005-2018) invocation syntax

`vfontas -D out/ -xf x.fnt` has become `vfontas -loadfnt x.fnt -saveclt out/`.

`vfontas -D out/ -cf x.fnt` has become `vfontas -loadclt out/ -savefnt x.fnt`.

`vfontas -Ecf x.fnt` has become `vfontas -blankfnt -savefnt x.fnt`.

`vfontas -G <x.fnt >x.psf` has become `vfontas -loadfnt x.fnt -canvas 9 16 -lge -savepsf2 x.psf`.

`vfontas -W <x.fnt >x.psf` has become `vfontas -loadfnt x.fnt -upscale 2 1 -savepsf2 x.psf`.

`vfontas --cpi -D out/ -f x.cpi/` has become `vfontas -xcpi x.cpi out/`.