make_sbix.py

import sys
from fontTools import ttLib
from fontTools.ttLib.tables import sbixStrike
from fontTools.ttLib.tables import sbixGlyph


ttfont = ttLib.TTFont()

# https://docs.microsoft.com/en-us/typography/opentype/spec/sbix
sbix = newTable("sbix")

# Apple Color Emoji.ttc has these bitmap strike sizes
# TODO add --bitmap-sizes option
bitmap_sizes = [20, 26, 32, 40, 48, 52, 64, 96, 160]
# Apple Emoji uses this
resolution = 72

# this can be also 'pdf', or special value 'dupe' which indicates that the
# imageData field contains a uint16, big-endian glyph ID.
# The bitmap data for the indicated glyph is used for the current glyph (a bit
# like composite glyphs in glyf table).
graphic_fype = "png"

for ppem in bitmap_sizes:
    strike = sbixStrike.Strike(ppem=ppem, resolution=resolution)
    # for each glyph...
    glyph_name = "a"
    # TODO: use cairosvg to rasterize svg to PNG at given sizes
    image_data = b"\0\0\0\0"

    strike.glyphs[glyph_name] = sbixGlyph.Glyph(
        glyphName=glyph_name,
        graphicType=graphic_fype,
        imageData=image_data,
        # these can be used to shift the bitmap image
        # originOffsetX=0,
        # originOffsetY=0,
    )

    sbix.strikes[ppem] = strike

ttfont["sbix"] = sbix