Print all the glyph 'master' locations from a variable TTF (user-scale coordinates).

get_gvar_masters.py

"""Print all the glyph 'master' locations from a variable TTF (user-scale coordinates).

A 'master' along a given axis is where a delta-set region peaks.
"""

from fontTools.varLib.models import piecewiseLinearMap


def map_axis_values(axis_mappings, location):
    return {
        axis: piecewiseLinearMap(value, axis_mappings[axis])
        for axis, value in location.items()
    }


def get_gvar_glyph_masters(gvar, axisTags, glyphName):
    default = {axisTag: 0.0 for axisTag in axisTags}
    masters = [default]
    for var in gvar.variations[glyphName]:
        masters.append(
            {
                **default,
                **{axis: peak for axis, (start, peak, end) in var.axes.items()},
            }
        )
    return masters


def get_all_gvar_masters(ttf, asUserSpace=True):
    fvar = ttf["fvar"]

    reverseFvarMaps = {
        a.axisTag: {-1: a.minValue, 0: a.defaultValue, 1: a.maxValue} for a in fvar.axes
    }
    axisTags = list(reverseFvarMaps.keys())

    reverseAvarMaps = None
    if asUserSpace and "avar" in ttf:
        avar = ttf["avar"]
        reverseAvarMaps = {
            k: {v: k for k, v in avar.segments[k].items()} for k in avar.segments.keys()
        }

    gvar = ttf["gvar"]
    result = {}
    for glyphName in gvar.variations.keys():
        masters = get_gvar_glyph_masters(gvar, axisTags, glyphName)

        if asUserSpace:
            if reverseAvarMaps:
                masters = (map_axis_values(reverseAvarMaps, loc) for loc in masters)
            masters = [map_axis_values(reverseFvarMaps, loc) for loc in masters]

        result[glyphName] = masters
    return result


if __name__ == "__main__":
    import sys
    from pprint import pprint
    from fontTools.ttLib import TTFont

    ttf = TTFont(sys.argv[1])

    gvar_masters = get_all_gvar_masters(ttf, asUserSpace=True)

    max_per_glyph_masters = max(len(masters) for masters in gvar_masters.values())
    print(max_per_glyph_masters)

    pprint(gvar_masters)