vfontas — a bitmap font file transformation utility
vfontas 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
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 outline fonts from bitmapped fonts.
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 FontForge.
vfontas offers the CLT bitmap format, wherein glyphs are represented as
textgraphical files to facilitate editing with terminal editors.
A bitmap font which is offered by its authors in multiple sizes can not only
constitute different sizes, but also visually different styles, similar to
what italic fonts are to regular fonts (e.g. longer descenders, more bulbous
terminals, etc.).
When vfontas converts bitmap fonts to vector, the "size" of a bitmap
font becomes "resolution". An 8x8 bitmap font and an 8x16 bitmap
font, after conversion to SFD and other vector formats
will have the
same height when the user requests such vectorized forms to be rendered in
size 12pt.
Pixel-perfect rendering of a (vectorized) bitmap font requires taking the
original size in px and applying the monitor DPI. A 16px tall font on a system
which uses a 96dpi setting displays well using 12pt or multiples thereof.
(16*72/96=12). Here is a cheat table for some font heights:
| BM Height |
96dpi |
x2 |
120dpi |
x2 |
| 13px |
9.75pt |
19.5pt |
7.8pt |
15.6pt |
| 14px |
10.5pt |
21pt |
8.4pt |
16.8pt |
| 15px |
11.25pt |
22.5pt |
9pt |
18pt |
| 16px |
12pt |
24pt |
9.6pt |
19.2pt |
| 18px |
13.5pt |
27pt |
10.8pt |
21.6pt |
| 20px |
15pt |
30pt |
12pt |
24pt |
| 22px |
16.5pt |
|
13.2pt |
26.4pt |
| 24px |
18pt |
|
14.4pt |
28.8pt |
| 28px |
21pt |
|
16.8pt |
|
| 32px |
24pt |
|
19.2pt |
|
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 |
Cell size |
Resolution |
VStretch |
| 40x25 |
8x8 |
320x200 |
6/5 = 1.2 |
| 80x25 |
8x8 |
640x200 |
12/5 = 2.4 |
| 80x25 |
8x14 |
640x350 |
48/35 = 1.37 |
| 80x25 |
9x14 |
720x350 |
54/35 = 1.54 |
| 80x25 |
9x16 |
720x400 |
27/20 = 1.35 |
| 80x30 |
8x16 |
640x480 |
1.0 |
| 80x43 |
8x8 |
640x350 |
48/35 = 1.37 |
| 80x50 |
8x8 |
640x400 |
6/5 = 1.2 |
|
|
x*y |
x*y/3*4 |
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.
Enlarges the glyph box to the specified size. (It never shrinks it.)
Discards the in-memory glyph index <-> Unicode mapping table.
Removes an outer area from the glyph images, shrinking the image in the process.
Mirrors/flips glyphs.
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.
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).
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.
Reads a BDF (Adobe Glyph Bitmap Distribution Format) font file.
Reads a directory full of CLT files containing glyphs. CLT is a textgraphical
format to facilitate visual editing with a text console editor.
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.
Reads a headerless bitmap font file, using the specified height N and width 8.
The number of characters is then autoderived from the filesize.
Reads a Unifont .hex encoded file.
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.
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.
Shift all glyphs by the given x/y offsets within their existing glyph box
(possibly truncating them).
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.)
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.
Saves the current in-memory glyphs to the given file, using the headerless
format.
Saves the current in-memory Unicode mapping table to the given file.
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.
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 +/- 3 edge segments,
which is somewhat comparable to a set of bitmap matrices (of size 7x2, 6x3,
5x4, 4x5, 3x6, 2x7). 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.
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.
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.
For BDF/SFD output: Declare the font as being bold.
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.)
Sets a specific property for SFD fonts (also partly used by BDF). Only a limited
set of
key names are recognized.
- FamilyName
- BDF: The value is used for the FAMILY_NAME attribute.
SFD: The value is influential for font selection UIs. A fontface's
regular/medium/bold/italic variants should carry the same FamilyName.
- FontName
- The PostScript font name. For BDF, this name will be used
to construct the X Logical Font Description (XLFD), i.e. the unwieldly
"-misc-FontName-medium-r-normal--0-0-75-75-c-10-iso10646-1"
string.
- FullName
- BDF: The values is used for the FONT attribute
SFD: The value should be the FamilyName joined by the name of the variant
(Regular/Medium, Bold, Italic, etc.). By convention, the regular/medium
variant is allowed to be represented without a specific variant name. In
other words, using {MyFont; MyFont Bold} or {MyFont Regular; MyFont Bold}
as the names for a font project with two thicknesses is up to the
user.
- ssf
- This special property controls the horizontal scaling of
all coordinates, but not the font's em size. The default value is
1/1. This setting is useful for implementing the correction
mentioned in the "Aspect ratio" section. Applying the
80x25@720x400 correction for example requires the use of the value
20/27.
- TTFWeight
- BDF: for the WEIGHT attribute; should be a numeric value
between 1-1000.
- Weight
- BDF: The values is used for the WEIGHT_NAME attribute.
SFD: A non-empty variant name, in lower case. ("medium",
"bold", ...)
Performs a linear upscale by an integral factor for all glyphs.
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.
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.
The Linux kernel accepts console font glyphs of at most 32x32 in size.
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
..................
....##....##..##..
..##..##..##..##..
..##..##..####....
..##..##..##..##..
....##....##..##..
..................
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"
`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/`.
hxtools(7)