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Guidelines for Writing System Support: Technical Details: Glyph Design
UNESCO project Initiative B@bel
A complete index of all SIL's contributions to UNESCO‘s project Initiative B@bel can be found here.
Guidelines Table of Contents
Section 1: Components of a Writing System Implementation
Section 2: The Process of WSI Development
Section 5: Technical Details: Characters, Codepoints, Glyphs
Section 6: Technical Details: Encoding and Unicode
Section 7: Technical Details: Data Entry and Editing
Section 8: Technical Details: Glyph Design
Section 9: Technical Details: Smart Rendering
The most basic computing need for a given writing system is a font. Without one, a WSI cannot exist, and the quality and accuracy of the letters is commonly how WSIs are judged. This section addresses the need for quality fonts and how they can be obtained, developed and improved. Specifics about “smart” fonts and their behavior are covered in Section 9. A general glossary of font terminology can be found on the Microsoft Typography web site.
8.1 Basic font requirements
The purpose of a font is to correctly display text in a language using the appropriate writing system. At a minimum, this requires the font to be complete and accurate for the language(s) covered by the font. Technically, this means that a font must:
8.2 The need for quality
WSIs are typically created by programmers or linguists, not typeface designers. Even though the computational complexity required to make a WSI work may be impressive, most WSIs suffer from fonts that are poor in quality, and may result in documents that are difficult or unpleasant to read. This is because most of the typeface design is done by those untrained in the task.
Typeface design is a subtle art, and the details of how lettershapes are shaped and interact are complex. So it is very valuable to consult experienced designers in the development of a WSI, and integrate their recommendations into the implementation.
It is a mistake to assume that language communities with little experience in technology will be satisfied with anything that only somewhat resembles their script. On the contrary, these readers are often more sophisticated and exacting than their counterparts who use the Latin script. For example, in Asia, there is a long history of writing, literacy and literature in many beautiful, indigenous scripts. Because of this strong manuscript tradition, the expectation is that fonts ought to closely follow traditional shapes. Yes, there is openness to modern interpretations, and a recognition of technical limitations, but satisfaction is usually linked with how faithfully the design echoes the tradition.
The history of Bengali typefaces illustrates this phenomenon. Bengali type has been available since 1778, and the printed history of the script is full of attempts to recreate the characteristic shapes with new technology. By the mid-20th century, the major font foundries, Monotype and Linotype, had systems that could typeset books and newspapers successfully. But both, and the Linotype in particular, had to make significant compromises in the rendering of the script due to technical limitations. Nevertheless, the general Bengali population seemed satisfied with the result. When new technology became available in the late 1970s, Linotype developed a new typeface that recreated the traditional style and forms that hearkened back to the manuscript tradition. Despite predictions that no one would accept it—they seemed satisfied with what they had—it became very successful and is now considered to be the definitive design for Bengali fonts. Nothing else is generally accepted for text material.1
WSI development needs to take into account the need for typefaces that accurately reflect the writing style and acknowledge the written history of the script. Because of the complex tools and subtle design sense required to create fonts, it is a specialized craft. Rarely do those who develop keyboards, encoding systems and other programmatic WSI components have the skills and training necessary, and so they must look elsewhere for fonts.
8.3 Sources for fonts
So where can quality typefaces be found? Traditional foundries as well as individual developers have designed good fonts for non-Latin writing systems. Generally, those companies with a long tradition of quality design offer the best fonts, but charge accordingly for them. Free fonts can be found all over the internet, but most lack in completeness and overall quality. There are exceptions to both of these, so it is worth investigating a variety of sources.
8.3.1 Commercial companies
Most commercial font vendors are not multi-faceted corporations, but are smaller companies focused solely on font development. As such, they rely on sales of their typefaces as their primary income source. Hence, their products can be expensive, and incorporation of their fonts in other WSIs requires payment of significant licensing fees. Their fonts are usually of good quality, though, and have high acceptance within language communities. Some of these companies are:
8.3.2 Public and not-for-profit
An alternative to commercial fonts are those developed by public and non-for-profit agencies. The goal of these groups is to enable technological advancement and literature production in both majority and minority writing systems. Their fonts are generally free for individual use, but may require modest licensing fees for inclusion in third-party WSIs. Font quality among these groups varies widely, but is often good. Because of their close association with language communities, these agencies tend to develop products that accurately reflect linguistic needs and preferences, and meet practical publishing needs.
There are only a few instances where governments have specifically developed and distributed fonts, but government-sponsored agencies can have an active role. The National Electronics and Computer Technology Center (NECTEC) in Thailand has led many of the computing efforts in that country, and has developed fonts that match the preferred style for text publishing.
More work is done by NGOs. These organizations range in size from small to large, and those differences are reflected in how widely their fonts are known. Many NGO fonts are developed and deployed locally, usually by untrained designers, and are not known outside of the language communities. Larger groups, such as SIL International3, have a broader scope, have greater resources (including trained designers), and are able to take on major font development projects.
Although most public and not-for-profit fonts are inexpensive or free, there is also a large and growing body of freeware and shareware fonts developed by individuals and distributed over the internet. Most of these are incomplete, inaccurate, of poor design quality, or do not function correctly, and are poor choices for inclusion in WSIs.
A small subset of these fonts, however, may be suitable. Internet searches can be successful in finding freeware fonts, and may even bring up reviews or comments on specific fonts. There are also many guides to non-Western fonts; three of these are:
8.3.4 Intellectual property and copyright issues
One of the challenges of incorporating third-party fonts in WSIs relates to intellectual property and copyright issues. It is not always easy to determine the true source of a font design. Many fonts on the internet are simply illegal versions of commercial fonts. So it is important to look at the copyright notice within the fonts, and even ask the developer where the design originated.
Fonts often need modification to work with a specific WSI or to meet the needs of a specific language community. It is important to know the licensing restrictions of any fonts that are modified. Many commercial and some public groups prohibit any modification, however minor. Others give their fonts very broad, open-source-style licensing.
The related paper “Intellectual Property Concerns in the Development of Complex Script and Language Resources” gives much more detail on these issues and discusses the unique nature of fonts as both works of art and pieces of computer software.
8.4 Process of font development
Despite the wide variety of fonts available from commercial and non-commercial sources, there remain situations where a new font design is needed. No font may exist, or those that are available may be inappropriate because of style or quality. There also may be licensing restrictions that hinder the use or modification of a particular font.
If significant funding is available, fonts can be commissioned from professional designers. Traditional foundries, such as Monotype, have a long history of this, but most recent commissions go to individuals or small foundries such as Tiro Typeworks, who are known for a specific area of expertise. Internet mailing lists, such as TYPO-L and Type-Design can also be a means to find designers interested in work, and professional associations such as ATypI can help.
The font development process, whether done by a foundry or by an individual, is similar to the WSI development process outlined in Section 2.
8.4.1 Initial research and planning
Careful planning is important to a font project’s success. Because the designer is often someone without an intimate knowledge of the writing system, they need reliable information from others about letter shapes, style and behavior. The basic steps are to:
Determine detailed needs. A font project needs a clear specification of all the glyphs needed and how they are to be encoded. This description will likely change as more information is discovered, but some initial listing is useful. The designer will also need to know how the glyphs are to interact with one another: how diacritics relate to base characters, common and uncommon letter combinations, etc. An orthography description, if available, can be very helpful.
Identify key script experts. The most important source for script information is the language community itself and the script experts within. These should be people whom the community recognizes as authoritative with regard to the written language—scribes, teachers, leaders, artists. Ongoing interaction with these experts can ensure that the font accurately reflects the writing system and meets the needs of the community.
Gather other sources and references. It is not enough to simply talk with script experts. Samples of the writing system are needed. There should be a variety of these—handwritten samples, school primers, existing books—and the script experts should give their opinion on which are the most ‘correct’. The internet can also be a source of information, but is often misleading or wrong. Published books and academic research are often more reliable and can provide useful historical background. Finally, electronic versions of authentic text material (folktales, etc.), if they exist, can be useful in testing.
Make style decisions. Most language communities would love to have more than a single style of font for their use. This raises priority questions and requires some additional investigation. What will be the primary use of the font—long document publishing, literacy primers, signage, on-screen reading (such as on the internet)? The use should be reflected in the style of the font. Tradition is also important. Is an ‘italic’ version needed for a script with no history of slanted forms? The answer is sometimes yes and sometimes no. For example, the Ethiopic script traditionally has a single style of letterform, a bold letter with calligraphic elements. Is it appropriate to create an italic version? And is an even bolder form even conceivable? There is no tradition of this, but the availability of the Bold and Italic buttons in word processing applications encourages users to desire these modern variants.
8.4.2 Glyph design procedures
Once planning is complete, and key style decisions are made, the design of glyphs can begin. Designers vary in their preferred design process. Some draw their glyphs directly on screen, while others prefer to draw shapes on paper and then bring them into the computer. In order to give a complete picture of what could be involved in the design process, the latter situation is described here. This is, again, only an example of the process and is not a definitive method.
Drawing. After study of the writing system, and the intended use for the font, the designer draws tentative lettershapes on paper, with a height of typically 2-5 cm. The lettershapes may be drawn as complete words, as an alphabet sample, or as seemingly random combinations of letters. The main goal is not to create final, perfect forms, but to experiment with stroke weights, terminal designs, initial spacing and general proportions.
Scanning. Once these initial shapes have been drawn, they are scanned into the computer, preferably at a resolution of approximately 300-400 pixels in height. Any scanning software would work for this, as long as the scanned image can be cropped and imported into the font design package. Detailed instructions on how prepare, scan and import images into the Macromedia Fontographer font design program can be found in Scanning Tips.
Initial digital outlines. Digital fonts are typically described not in terms of pixels, but as mathematical curves that define the outline of the glyph. So the scanned images are used only as a guideline for the preparation of the outlines. Once the scanned images are imported into the font design application, the designer can begin to draw initial outlines of a few key glyphs, based generally on the drawn and scanned shapes. These are tentative, and will likely be changed throughout the next step.
Refining parameters. After the basic shapes have been drawn, the designer can create draft fonts in order to test glyph size, weight, etc., and then revise the draft shapes repeatedly until they look generally correct. At the end of this process, there should be specific parameters determined for the font—letter height, stroke widths, length of serifs, amount of contrast, and other numeric guidelines.
Completing the glyph set. The next step is to design the remaining glyphs, based upon the style and parameters of the initial key glyphs.
Adjusting spacing. Good spacing can improve a mediocre typeface, but bad spacing can ruin a beautiful one. Great care must be taken to ensure that letters are spaced properly. This includes kerning for pairs of letters that, because of their design, would run into one another or leave large gaps of whitespace between them. The goal is to create a flowing, uninterrupted line of text with even texture. This is important for readability, especially for beginning readers.
Hinting. Legibility of letters on computer screens, or on low-resolution printing devices, is heavily dependent on ‘hints’ contained in the font4. These are special computer instructions that specify how the mathematical outlines are turned into pixels. Hinting is a highly technical task, and most independent designers avoid it due to the time and expertise it requires. Modern font development applications include auto-hinting routines that can improve a font’s appearance on screen, but the results are not as good as manual hinting. For more discussion on hinting strategies, see Notes on Hinting with FontLab.
Packaging and distribution. This involves packaging the font and any related documentation and instructions for the user or for those who are building the font into a larger WSI or software application.
Although testing is usually done throughout the whole font design process, it also needs to be done once the font is generally completed, with all glyphs designed and spaced. There are four kinds of testing:
Fonts are critical WSI components. Font design, however, is a complicated task, and requires artistic as well as analytical skills. Most WSI developers do not have the expertise to design their own fonts, and need to look to other sources. There are many companies and individuals who will license fonts and even prepare new designs on commission. Despite this, it is sometimes necessary for a WSI developer to take on the task.
8.6 Sources for information
The following are sources for information on fonts and typeface design.
Many of these tools come from FontLab Ltd., a company that has become the main font tool provider for the font design industry.
DTL Fontmaster—specialized, but expensive tools for design and font production
Font Creator—a little known, and limited, TrueType font editor
FontLab—the font design tool that has become the industry standard
Fontographer—this was the main design tool, but has not been updated in many years and is rapidly becoming obsolete
Scanfont—a tool for scanning drawn glyphs and importing them into FontLab
TransType—a font converter
TypeTool—a lightweight, and cheaper, version of FontLab
Microsoft and Apple also provide font development tools on their Web sites. See section 8.6.2.
A large number of copyleft, FLOSS and open source tools are listed in Resources for Writing Systems Implementation using Copyleft and FLOSS (Free/Libre and Open Source Software).
8.6.2 Web sites
Adobe Type Topics—a variety of information on Adobe fonts and general type issues
Apple Fonts/Tools—technical information and tools from Apple Computer
Microsoft Typography—excellent site about the technical aspects of type design and Microsoft’s tools
TrueType Typography—general information about the TrueType font format
Bringhurst, Robert, The elements of typographic style. (2nd ed), Point Roberts: WA, Hartley & Marks, 1996. This is a general reference to use of fonts and type, but can be useful to anyone studying design.
Moye, Stephen, Fontographer: type by design. MIS Press, 1995. Though out of print, this book is a useful guide to type design processes. It is specifically for Fontographer, but can be applicable to other tools.
Tracy, Walter, Letters of credit: a view of type design. London: Gordon Fraser, 1986. This is the best book on the foundational concepts behind type design, and gives particularly good advice on spacing Latin fonts.
The TypeBooks web site is a good source for books and reviews.
[ROS1999] Fiona Ross, The Printed Bengali Character and its Evolution.London: Curzon Press, 1999.
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