Comparison of 'glyf', 'CFF ' and CFF2 tables

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Editor’s note: This is a pre-release draft for OpenType 1.9.1. Changes shown here reflect changes from version 1.9 of the OpenType spec.

Status: This is a pre-release draft for OpenType 1.9.1, published to facilitate wide review. The content may be updated or replaced at any time before OpenType 1.9.1 is released. It is inappropriate to cite this other than as work in progress.

Editor's note: This page is being newly added in OpenType 1.9.1.

Three alternate formats are available for storing monochrome glyph outlines in OpenType fonts: the 'glyf' table, the 'CFF ' table, and the CFF2 table. A functioning OpenType font must contain one of these tables. This section provides a comparison of these alternate formats for glyph data.

CFF2 and CFF use cubic (3rd order) Bézier curves to represent glyph outlines, whereas the 'glyf' table uses quadratic (2nd order) Bézier curves. CFF2 and CFF also use a different conceptual model for “hints” than the 'glyf' table. The three tables also differ in relation to support of variations and in how variation data is stored.

The following table provides a summary comparison of the CFF2, 'CFF ' and 'glyf' tables. Note that some of these differences might not be exposed in high-level font editing software or in runtime programming interfaces.

Consideration glyf CFF CFF2
curves quadratic (2nd order) Bézier cubic (3rd order) Bézier cubic (3rd order) Bézier
coordinate precision 1 FUnit 1/65536 FUnit 1/65536 FUnit
hinting TrueType instructions move outline points by controlled amounts alignment zones apply to all glyphs, stem locations are declared in each glyph alignment zones apply to all glyphs, stem locations are declared in each glyph
decoding not stack-based (except TrueType instructions) mostly stack-based mostly stack-based
OpenType variations supported: outline variation data is stored in the 'gvar' table (OFF: 7.3.4); hint variation data is stored in the 'cvar' table (OFF: 7.3.2) not supported supported: variation data for outlines and hints is stored within the CFF2 table, partially using common formats for variation data also used in other tables, and partially interleaved within the CharString data for individual glyph descriptions
data redundancy low moderate low
overlapping contours supported not supported supported