Unfortunately every system has its own way of storing bitmap only fonts into an sfnt wrapper (or the system just doesn't support it)
Apple documents the existence of a bitmap only format, and gives some hints about the requirements of it. Their documentation is far from complete and the following is determined in part by that documentation, in part by examining the (few) bitmap only fonts of theirs I have found, and in part by error messages given by some of their tools.
bloc'
and
'bdat'
tables.EBLC'
and
'EBDT'
tables used in OpenType)
head'
table is replaced by a
'bhed'
table which is byte for byte identical
glyf',
'loca'
nor 'CFF ' tables.
hhea' nor 'hmtx' tables (metrics
data are provided in the bitmap strikes themselves)
vhea' nor 'vmtx' tables
either)
maxp'.numGlyphs
is set to the number of bitmap glyphs
The X consortium have devised their own format which they call "OpenType Bitmap" with extension .otb.
EBLC'
and
'EBDT'
tables.
glyf'
table
loca'
table with one entry in it
head'
table (not a 'bhed')
maxp'.numGlyphs
is set to the number of bitmap glyphs, not to the size of the
'loca'
table
MicroSoft Windows provides no support for a bitmap only sfnt. So I have created a faked up format which should work in most cases
EBLC'
and
'EBDT'
tables.
glyf'
/
'loca'
tables with entries for every glyph. If used the entries will produce blank
glyphs (spaces).
EBSC'
table which maps common pixel sizes to the supplied pixel sizes. (so if a
user asked for a 20 pixel strike s/he might get an 18 pixel strike -- as
opposed to getting a set of blanks.
head'
table (not a 'bhed')