font::ttf::glyph(3)
NAME
Font::TTF::Glyph - Holds a single glyph's information
DESCRIPTION
This is a single glyph description as held in a TT font.
On creation only its header is read. Thus you can get the
bounding box of each glyph without having to read all the
other information.
INSTANCE VARIABLES
In addition to the named variables in a glyph header
("xMin" etc.), there are also all capital instance vari
ables for holding working information, mostly from the
location table.
- The standard attributes each glyph has are:
- numberOfContours
xMin
yMin
xMax
yMax - There are also other, derived, instance variables for each
glyph which are read when the whole glyph is read (via
"read_dat"): - instLen
- Number of bytes in the hinting instructions (Warning
this variable is deprecated, use
"length($g-"{'hints'})> instead). - hints
- The string containing the hinting code for the glyph
- In addition there are other attribute like instance vari
ables for simple glyphs:
For each contour there is:- endPoints
An array of endpoints for each contour in the
glyph. There are "numberOfContours" contours in a
glyph. The number of points in a glyph is equal to
the highest endpoint of a contour. - There are also a number of arrays indexed by point
number - flags
The flags associated with reading this point. The
flags for a point are recalculated for a point
when it is "update"d. Thus the flags are not very
useful. The only important bit is bit 0 which
indicates whether the point is an 'on' curve
point, or an 'off' curve point. - x The absolute x co-ordinate of the point.
- y The absolute y co-ordinate of the point
- For composite glyphs there are other variables
- metric
- This holds the component number (not its glyph number)
of the component from which the metrics for this glyph
should be taken. - comps
- This is an array of hashes for each component. Each
hash has a number of elements: - glyph
The glyph number of the glyph which comprises this
component of the composite. - args
An array of two arguments which may be an x, y coordinate or two attachment points (one on the base
glyph the other on the component). See flags for
details. - flag
The flag for this component
- scale
A 4 number array for component scaling. This
allows stretching, rotating, etc. Note that scal
ing applies to placement co-ordinates (rather than
attachment points) before locating rather than
after. - numPoints
- This is a generated value which contains the number of
components read in for this compound glyph. - The private instance variables are:
- INFILE (P)
- The input file form which to read any information
- LOC (P)
- Location relative to the start of the glyf table in
the read file - BASE (P)
- The location of the glyf table in the read file
- LEN (P)
- This is the number of bytes required by the glyph. It
should be kept up to date by calling the "update"
method whenever any of the glyph content changes. - OUTLOC (P)
- Location relative to the start of the glyf table. This
variable is only active whilst the output process is
going on. It is used to inform the location table
where the glyph's location is, since the glyf table is
output before the loca table due to alphabetical
ordering. - OUTLEN (P)
- This indicates the length of the glyph data when it is
output. This more accurately reflects the internal
memory form than the "LEN" variable which only
reflects the read file length. The "OUTLEN" variable
is only set after calling "out" or "out_dat". - Editing
- If you want to edit a glyph in some way, then you should
read_dat the glyph, then make your changes and then update
the glyph or set the $g->{' isdirty'} variable. It is the
application's duty to ensure that the following instance
variables are correct, from which update will calculate
the rest, including the bounding box information.
numPoints
numberOfContours
endPoints
x, y, flags (only flags bit 0)
instLen
hints- For components, the numPoints, x, y, endPoints & flags are
not required but the following information is required for
each component.
flag (bits 2, 10, 11, 12)
glyph
args
scale
metric (glyph instance variable)
METHODS Font::TTF::Glyph->new(%parms)
Creates a new glyph setting various instance variables
$g->read
Reads the header component of the glyph (bounding box,
etc.) and also the glyph content, but into a data field
rather than breaking it down into its constituent struc
tures. Use read_dat for this.
$g->read_dat
Reads the contents of the glyph (components and curves,
etc.) from the memory store "DAT" into structures within
the object. Then, to indicate where the master form of the
data is, it deletes the "DAT" instance variable.
$g->out($fh)
Writes the glyph data to outfile
$g->out_xml($context, $depth)
Outputs an XML description of the glyph
$g->update
Generates a "$self-"{'DAT'}> from the internal structures,
if the data has been read into structures in the first
place. If you are building a glyph from scratch you will
need to set the instance variable ' read' to 2 (or some
thing > 1) for the update to work.
$g->update_bbox
Updates the bounding box for this glyph according to the
points in the glyph
$g->maxInfo
Returns lots of information about a glyph so that the
"maxp" table can update itself.
$g->empty
Empties the glyph of all information to the level of not
having been read. Useful for saving memory in apps with
many glyphs being read
$g->get_points
This method creates point information for a compound
glyph. The information is stored in the same place as if
the glyph was not a compound, but since numberOfContours
is negative, the glyph is still marked as being a compound
$g->get_refs
Returns an array of all the glyph ids that are used to
make up this glyph. That is all the compounds and their
references and so on. If this glyph is not a compound,
then returns an empty array
BUGS
- · The instance variables used here are somewhat clunky
- and inconsistent with the other tables.
- · "update" doesn't re-calculate the bounding box or
- "numberOfContours".
AUTHOR
- Martin Hosken Martin_Hosken@sil.org. See Font::TTF::Font
for copyright and licensing.