Colour glyphs using the CBDT/CBLC tables are PNG images embedded instead of vector glyphs, using tables designed by Google. They should be supported by FreeType already, though this requires enabling the png option, which we don't do to avoid bundling the libpng library.

An alternative may be instead of going through FreeType+libpng, we can still extract the glyph data and pass it to Pillow. Hopefully this is possible, but I have not investigated it fully.

Note that as these are bitmaps, they require some special handling to render at arbitrary sizes, and we do not currently support bitmap fonts at all.