Open Source And Free Software Fonts

Cross Breeding Fonts

One quality of Libre fonts is that they can be readily developed from other Libre fonts, unhindered by the licensing restrictions used by proprietary fonts. One method of developing new fonts is simply to cross breed them. For example, Tienne is a display and text serif webfont being designed from the mixing of ‘font dna’ between Artifika font by Cyreal and Ascender Corp’s Droid Serif font.

An example process for breeding webfonts

The outlines of Artifika and Droid Serif were first converted to UFO format and then the curves made ‘interpolation compatible’ using Type Supply’s Prepolator software. Successful interpolation relies on any two shapes to be blended having the same number of points and the same direction of curves. Prepolator provides a graphical interface to add and remove points, and to check the compatibility of each glyph. Once ready, the forms can be interpolated in Superpolator. The interpolation process ‘blends’ the 2 sets of font forms. This blending process can be controlled in a number of ways and can be kept straightforward, or can be made more complex by for example, adding more axiis. In the simple example below Droid Serif and Artikika are at positions 1 and 4. Interpolated between these poles are two sets of curves, 2 and 3. These two instances have been interpolated slightly differently. Instance 2 is at exactly 50% between the Droid Serif and Artifika. Instance 3 however has it’s horizontal at 42% interpolated and it’s vertical at 56% interpolated.

From experimenting with the curves of Droid Serif and Artifika in Superpolator a fairly rough set of new curves was produced that suggested a new (but still related) emerging font. In the example of Tienne the forms that came from interpolating between Artifika and Droid Serif were fairly mutated but there were enough forms emerging to suggest the new font. These new forms are now being reshaped to create what is becoming Tienne. A much heavier set of curves was also created from the same interpolations. Below is a heavy weight, upppercase ‘M’ glyph after interpolation (left) and after re-shaping (right).


At the moment there are 2 weights resulting from the interpolation process; regular and heavy. At it’s regular weight Tienne will hopefully make a workeable and attractive text face. The heavy weight in progress is aimed at becoming a poster-like display face. Once these 2 have a basic character set they can be interpolated to create intermediate weights such as medium, bold or black. The regular and heavy weights can also be extrapolated to seek out the more extreme skinny and poster weights a opposite end of the weight axis.

So Why do that?

Fonts are, amongst other things, very complex ‘visual tools’. Font choice changes the overall visual look of a page and that change occurs between even very similar looking fonts. This is especially true when dealing with body text; the reader sees a block of body text fundamentally as a visual object and not just as a collection of words, or meanings. Printers and typesetters have known this for generations, hence the large amount of text faces that have been created and put into use for hundreds of years. With the increasing adoption of webfonts giving greater font choice for web designers, the visual impact of pages can now also be varied more and more by making slight style variations via the use of different fonts. The more fonts are available, the more designers can concentrate on choosing the right font for a page. Designers actually need as many similar looking fonts as they need different looking fonts. One way to create these fonts fairly rapidly is to concentrate less on producing ‘originality’ and crossbreed fonts rather than building each new one from scratch. In fact type designers have been doing this for generations for the print presses; pure originality for it’s own sake pretty much always took second place to fulfilling the practical demands of print production. The same will be true for fonts used across the web.

The Uniqueness of ‘Tienne’

The differences between Droid Serif and Tienne, or, Artifika and Tienne may look at times minimal at the level of a single glyph, but when set as body text, the differences are intensified, see the screenshots below. A similar effect will also occur when the glyphs are enlarged to display sizes; at large sizes the differences between characters are magnified.  So at the level of a body of small text the effect of Tienne is somewhere between the visual effect of Droid Serif and Artifika. Tienne functions for the user very much like a ‘standard’ sans serif, but it carries an amount more ‘movement’ and ‘interest’ than Droid Serif as a result of the material it has inherited from Artifika. The font material that ends up in hybrid font s is either a % mix, such as the curve of bowls and curves, or specific features that appear less often through out a glyph or the whole font. If we look at the serifs for example, Tienne has more serifs than Artifika but less serifs than Droid Serif. Also the serif forms in Tienne are a % mix between the more angular serifs of Droid and the more organic, almost script-like, serif forms in Artifika. Those two differences alone are enough to create significant variation in a block of text or in a large display headline.


This sort of process can speed up production of new fonts and diversify font choice for web designers.

Interpolating fonts in this way still needs varying amounts of human decision making and designing, not only pre-interpolation, but during and after interpolation. In the case of Tienne the interpolated forms were often malformed so Tienne still needs much carefull redrawing by hand. For example the left hand stem of the ‘n’ character has a bottom serif in Droid Serif, wherease the ‘n’ of Artifika has no serif at all except some slight flaring and a the hint of an emerging serif on the right of the stem. interpolating fonts like this creates new font forms but it can’t create finished fonts.

Interpolating fonts with Prepolator and Superpolator can be much more tightly controlled than in the example above. With more strategic positioning of extra points in Prepolator the fonts resulting from the interpolation process will be less mutated. However when the interpolated glyphs  are allowed to ‘find their own forms’ there is chance that new form may emerge that may not have resulted if a more controlled approach was used. New forms can allways be reshaped and refined later.

Licensing Details

One of the keys of opensource software is that it’s licensing allows users to further develop the software. With fonts released under the Open Font License this allows anyone to edit the font-using font editing software and alter, extend, fix, break. However it is important to note that different opensource licenses give varied levels of freedom, so in general it makes best sense to cross breed an OFL font with another OFL font because whilst the font forms can be merged, the licensing details generally cannot.

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