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PDF::API2::Basic::TTF::Glyph
Holds a single glyph's information

PDF::API2::Basic::TTF::Glyph - Holds a single glyph's information


NAME

PDF::API2::Basic::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 variables 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 variables 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 updated. 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 co-ordinate 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 scaling 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)



=head1 METHODS

$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


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 the PDF::API2::Basic::TTF::Font manpage for copyright and licensing.

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