ufo2ft: A Python repository from Google Fonts

ufo2ft

ufo2ft ("UFO to FontTools") is a fork of ufo2fdk whose goal is to generate OpenType font binaries from UFOs without the FDK dependency.

The library provides two functions, compileOTF and compileTTF, which work exactly the same way:

from defcon import Font
from ufo2ft import compileOTF
ufo = Font('MyFont-Regular.ufo')
otf = compileOTF(ufo)
otf.save('MyFont-Regular.otf')

In most cases, the behavior of ufo2ft should match that of ufo2fdk, whose documentation is retained below (and hopefully is still accurate).

Naming Data

As with any OpenType compiler, you have to set the font naming data to a particular standard for your naming to be set correctly. In ufo2fdk, you can get away with setting two naming attributes in your font.info object for simple fonts:

familyName: The name for your family. For example, "My Garamond".
styleName: The style name for this particular font. For example, "Display Light Italic"

ufo2fdk will create all of the other naming data based on thse two fields. If you want to use the fully automatic naming system, all of the other name attributes should be set to None in your font. However, if you want to override the automated system at any level, you can specify particular naming attributes and ufo2fdk will honor your settings. You don't have to set all of the attributes, just the ones you don't want to be automated. For example, in the family "My Garamond" you have eight weights. It would be nice to style map the italics to the romans for each weight. To do this, in the individual romans and italics, you need to set the style mapping data. This is done through the styleMapFamilyName and styleMapStyleName attributes. In each of your roman and italic pairs you would do this:

My Garamond-Light.ufo

familyName = "My Garamond"
styleName = "Light"
styleMapFamilyName = "My Garamond Display Light"
styleMapStyleName = "regular"

My Garamond-Light Italic.ufo

familyName = "My Garamond"
styleName = "Display Light Italic"
styleMapFamilyName = "My Garamond Display Light"
styleMapStyleName = "italic"

My Garamond-Book.ufo

familyName = "My Garamond"
styleName = "Book"
styleMapFamilyName = "My Garamond Display Book"
styleMapStyleName = "regular"

My Garamond-Book Italic.ufo

familyName = "My Garamond"
styleName = "Display Book Italic"
styleMapFamilyName = "My Garamond Display Book"
styleMapStyleName = "italic"

etc.

Additionally, if you have defined any naming data, or any data for that matter, in table definitions within your font's features that data will be honored.

Feature generation

If your font's features do not contain kerning/mark/mkmk features, ufo2ft will create them based on your font's kerning/anchor data.

In addition to Adobe OpenType feature files, ufo2ft also supports the MTI/Monotype format. For example, a GPOS table in this format would be stored within the UFO at data/com.github.googlei18n.ufo2ft.mtiFeatures/GPOS.mti.

Fallbacks

Most of the fallbacks have static values. To see what is set for these, look at fontInfoData.py in the source code.

In some cases, the fallback values are dynamically generated from other data in the info object. These are handled internally with functions.

Merging TTX

If the UFO data directory has a com.github.fonttools.ttx folder with TTX files ending with .ttx, these will be merged in the generated font. The index TTX (generated when using using ttx -s) is not required.

Color fonts

ufo2ft supports building COLR and CPAL tables.

If there is com.github.googlei18n.ufo2ft.colorPalettes key in font lib, and com.github.googlei18n.ufo2ft.colorLayerMapping key in the font or in any of the glyphs lib, then ufo2ft will build CPAL table from the color palettes, and COLR table from the color layers.

colorPalettes is a array of palettes, each palette is a array of colors and each color is a array of floats representing RGBA colors. For example:

<key>com.github.googlei18n.ufo2ft.colorPalettes</key>
<array>
  <array>
    <array>
      <real>0.26</real>
      <real>0.0</real>
      <real>0.23</real>
      <real>1.0</real>
    </array>
    <array>
      <real>0.86</real>
      <real>0.73</real>
      <real>0.28</real>
      <real>1.0</real>
    </array>
  </array>
</array>

colorLayerMapping is a array of color layers, each color layer is a array of layer name and palette color index. It is a per-glyph key, but if present in the font lib then it will be used for all glyphs that lack it. For example:

<key>com.github.googlei18n.ufo2ft.colorLayerMapping</key>
<array>
  <array>
    <string>color.1</string>
    <integer>1</integer>
  </array>
  <array>
    <string>color.2</string>
    <integer>0</integer>
  </array>
</array>

With these this key present, ufo2ft will copy the color layers into individual glyphs and setup COLR table.

Alternatively, if the color layers are already separate UFO glyphs, the com.github.googlei18n.ufo2ft.colorLayers font lib key can be used. It uses a table keyed by base glyph, and the value is an array of color layers, each color layer is an array of glyph name and palette color index. For example:

<key>com.github.googlei18n.ufo2ft.colorLayers</key>
<dict>
  <key>alef-ar</key>
  <array>
    <array>
      <string>alef-ar.color0</string>
      <integer>2</integer>
    </array>
  </array>
  <key>alefHamzaabove-ar</key>
  <array>
    <array>
      <string>alefHamzaabove-ar.color0</string>
      <integer>1</integer>
    </array>
    <array>
      <string>alefHamzaabove-ar.color1</string>
      <integer>2</integer>
    </array>
  </array>
<dict>

Setup Notes

If you are installing ufo2ft from source, note that the strict dependency versions in requirements.txt are for testing, see setup.py's install_requires and extras_requires for more relaxed dependency requirements.