GNU Unifont

The Unicode Basic Multilingual Plane covers 2¹⁶ (65,536) code points. Of this number, 2,048 are reserved for special use as UTF-16 surrogate pairs and 6,400 are reserved for private use. This leaves 57,088 code points to which glyphs can be assigned. Some of these code points are special values that do not have an assigned glyph, but most do have assigned glyphs.

As of May 2019, the GNU Unifont has complete coverage of the Basic Multilingual Plane as defined in Unicode 12.1.0. Its companion fonts, Unifont Upper and Unifont CSUR, have significant coverage of the Supplementary Multilingual Plane and the ConScript Unicode Registry, respectively.

For version 12.1.02, Unifont JP was released, which covers 10,000 Japanese kanji present in the JIS X 0213 character set, some of which are in the Supplementary Ideographic Plane. It is derived from Jiskan16, a public domain font.

Scripts that are less than 100% complete can be augmented by any contributor.

The large block of about 20,000 CJK ideographs has been copied from WenQuanYi's Unibit font with permission.[1]^{(Wen Quan Yi: Spring of Letters)}

However, despite its coverage, Unifont stores only one glyph per printable Unicode code point. So it does not feature the OpenType features needed to render correctly scripts with complex layouts (notably Indic scripts), and correctly position the combining diacritics with base letters if these combinations are not encoded in Unicode in their precombined form; as well the contextual forms (including joining types, and subjoined clusters) are not handled: this would increase the number of glyphs to include in the basic font and it's still not possible (because of current OpenType limitations) to encode all the needed glyphs to represent all the required combinations that can exist in a single Unicode plane (this is also true for Chinese fonts that cannot cover completely all ideograms currently encoded in two planes, and also in a third plane starting with the next 13.0 version of Unicode). Such font can then only be used as a "last resort" default font, suitable for simple alphabetic scripts, or to render isolated characters, but will make actual texts difficult or sometimes impossible to read correctly. For correctly rendering Indic abugidas (and Semitic abjads if they are written with their optional combining diacritics), other fonts should be specified in stylesheets before this one, and additional fonts will be needed to cover Han ideographs encoded in supplementary planes, or to render most historic (or minority modern) scripts not encoded in the BMP.

Sample in Japanese and Chinese

Unifont, as of version 12.0.0, is available in vector TTF, BDF, and PCF formats for the "standard build". Only the TrueType build is split into Unifont and two companion fonts.[1]

A few "specialized versions" have been built by request and made available by Paul Hardy. These include a bitmap TTF (SBIT) with empty glyphs filled with code-point values for FontForge users to read, a PSF bitmap with glyphs for APL programmers, and single-file versions in Roman's .hex format (see below).[1] The actual organization of the source consists of smaller .hex files to be stitched together and converted to other formats in a build.[2]

The GNU Unifont .hex format defines its glyphs as either 8 or 16 pixels in width by 16 pixels in height. Most Western script glyphs can be defined as 8 pixels wide, while other glyphs (notably the Chinese–Japanese–Korean, or CJK set) are typically defined as 16 pixels wide.

The unifont.hex file contains one line for each glyph. Each line consists of a four-digit Unicode hexadecimal code point, a colon, and the bitmap string. The bit string is 32 hexadecimal digits for an 8-pixel-wide glyph or 64 hexadecimal digits for a 16-pixel-wide glyph. The goal is to create an intermediate format that would facilitate adding new glyphs.

A '1' bit in the bit string corresponds to an 'on' pixel. Pixels bits are stored top to bottom, left to right.

0041:0000000018242442427E424242420000

0041:	
	––––––––
	––––––––
	––––––––
	––––––––
	–––##–––
	––#––#––
	––#––#––
	–#––––#–
	–#––––#–
	–######–
	–#––––#–
	–#––––#–
	–#––––#–
	–#––––#–
	––––––––
	––––––––

0041:
	– – – – – – – –
	– – – – – – – –
	– – – – – – – –
	– – – – – – – –
	– – – # # – – –
	– – # – – # – –
	– – # – – # – –
	– # – – – – # –
	– # – – – – # –
	– # # # # # # –
	– # – – – – # –
	– # – – – – # –
	– # – – – – # –
	– # – – – – # –
	– – – – – – – –
	– – – – – – – –

Roman Czyborra created the Unifont format in 1998[4] after earlier efforts dating to 1994.

In 2008, Luis Alejandro González Miranda wrote a program to convert this font into a TrueType font. Paul Hardy modified it later to support combining characters in the TrueType version.

Finally, Richard Stallman dubbed Unifont a GNU package in October 2013, with Paul Hardy as its maintainer.

Wikimedia Commons has media related to GNU Unifont.

• GNU Project Archives
• Unifoundry.com GNU Unifont page