Font::TTF::OS_2

Section: User Contributed Perl Documentation (3)
Updated: 2021-01-27
Page Index

NAME

Font::TTF::OS_2 - the OS/2 table in a TTF font

DESCRIPTION

The OS/2 table has two versions and forms, one an extension of the other. This module supports both forms and the switching between them.

INSTANCE VARIABLES

No other variables than those in table and those in the standard:

    Version
    xAvgCharWidth
    usWeightClass
    usWidthClass
    fsType
    ySubscriptXSize
    ySubScriptYSize
    ySubscriptXOffset
    ySubscriptYOffset
    ySuperscriptXSize
    ySuperscriptYSize
    ySuperscriptXOffset
    ySuperscriptYOffset
    yStrikeoutSize
    yStrikeoutPosition
    sFamilyClass
    bFamilyType
    bSerifStyle
    bWeight
    bProportion
    bContrast
    bStrokeVariation
    bArmStyle
    bLetterform
    bMidline
    bXheight
    ulUnicodeRange1
    ulUnicodeRange2
    ulUnicodeRange3
    ulUnicodeRange4
    achVendID
    fsSelection
    usFirstCharIndex
    usLastCharIndex
    sTypoAscender
    sTypoDescender
    sTypoLineGap
    usWinAscent
    usWinDescent
    ulCodePageRange1
    ulCodePageRange2
    xHeight
    CapHeight
    defaultChar
    breakChar
    maxLookups

Notice that versions 0, 1, 2 & 3 of the table are supported. Notice also that the Panose variable has been broken down into its elements.

METHODS

$t->read

Reads in the various values from disk (see details of OS/2 table)

$t->out($fh)

Writes the table to a file either from memory or by copying.

$t->XML_element($context, $depth, $key, $value)

Tidies up the hex values to output them in hex

$t->XML_end($context, $tag, %attrs)

Now handle them on the way back in

$t->minsize()

Returns the minimum size this table can be. If it is smaller than this, then the table must be bad and should be deleted or whatever.

$t->update

Updates the OS/2 table by getting information from other sources:

Updates the "firstChar" and "lastChar" values based on the MS table in the cmap.

Updates the sTypoAscender, sTypoDescender & sTypoLineGap to be the same values as Ascender, Descender and Linegap from the hhea table (assuming it is dirty) and also sets usWinAscent to be the sum of Ascender+Linegap and usWinDescent to be the negative of Descender.

$t->guessRangeBits (\%map, [$cp_threshold, [%u_threshold]])

Set the ulCodePageRange and ulUnicodeRange fields based on characters actually present in the font.

%map is a hash keyed by USV returning non-zero for characters present (e.g. use {'val'} a from Unicode cmap).

The two optional parameters are percentage of characters within the codepage or unicode range that need to be present to constitute coverage. A threshold of 0 causes corresponding range bits to be set if any characters are present at all, while a negative value causes the corresponding range bits to be unchanged. Defaults are 50 and 0, respectively.

For codepage bits, the threshold is percentage of characters between 0xC0 and 0xFF that need to be present to constitute coverage). For codepages other than 1252, characters (e.g., punctuation) that are defined identically to cp1252 are ignored for the purposes of this percentage calculation. Looks only for SBCS codepages, not DBCS.

For Unicode range bits that represent multiple ranges, e.g., bit 29 represents:

  Latin Extended Additional  1E00-1EFF
  Latin Extended-C           2C60-2C7F
  Latin Extended-D           A720-A7FF

the bit will be set if any of these ranges meet the threshold requirement.

BUGS

None known

AUTHOR

Martin Hosken <http://scripts.sil.org/FontUtils>.

LICENSING

This module is released under the terms of the Artistic License 2.0. For details, see the full text of the license in the file LICENSE.