cidg: CID to Glyph ID table

The cidg table is an Apple Advanced Typography (AAT) table.

class fontTools.ttLib.tables._c_i_d_g.table__c_i_d_g(tag=None)[source]

Bases: BaseTTXConverter

CID to Glyph ID table

The AAT cidg table has almost the same structure as gidc, just mapping CIDs to GlyphIDs instead of the reverse direction.

It is useful for fonts that may be used by a PDF renderer in lieu of a font reference with a known glyph collection but no subsetted glyphs. For instance, a PDF can say “please use a font conforming to Adobe-Japan-1”; the cidg mapping is necessary if the font is, say, a TrueType font. gidc is lossy for this purpose and is obsoleted by cidg.

For example, the first font in /System/Library/Fonts/PingFang.ttc (which Apple ships pre-installed on MacOS 10.12.6) has a cidg table.

See also https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6gcid.html