# `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)

  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