Transformed ‘glyf’ table getting larger than the original

Is it normal that the transformed ‘glyf’ table (before compression) being
(much) larger than the original?

In SFNT-TTF.ttf[1] from the test suit, the original ‘glyf’ table is
712 bytes but the transformed table is 3706 bytes before compression,
i.e. more than 5 times the original size. I wasn’t expecting the
transformed tables to grow in size, let alone grow that much. I tested
with several implementations (mine, Google’s and FontTools) and all give
the same result. The only unusual aspect of that font is having a glyph
with a single contour containing 506 points (it was constructed that way
for the mustAccept255UInt16 test).

I’m just checking whether this is expected or not and what is the
table should be transformed or not in this case.

Regards,
Khaled

1. https://github.com/w3c/woff2-tests/blob/master/generators/resources/SFNT-TTF.ttf
2. https://www.w3.org/Fonts/WG/wiki/TestPlan20-UserAgent#mustAccept255UInt16

Received on Monday, 15 August 2016 09:36:44 UTC