[Raku HarfBuzz Project] / [HarfBuzz-Subset Module]

HarfBuzz-Subset-raku

Description

Bindings to the HarfBuzz Subset font subsetting library.

This module is classed as Experimental, just because a recent HarfBuzz 3.0.0+ library needs to be built with the latest harfbuzz-subset library.

Synopsis

use HarfBuzz::Subset;

# face to be subsetted
my $file = "t/fonts/NimbusRoman-Regular.otf";

my @unicodes = 'Hello, World!'.ords;
my HarfBuzz::Subset $subset .= new: :face{ :$file }, :input{ :@unicodes };
my Blob() $buf = $subset;
'/tmp/my-nimbus-subset.otf'.IO.spurt: :bin, $buf;

Description

This module binds to the HarfBuzz library's subsetting capability and allows a font to be compacted to a smaller set of glyphs.

Subsetting is useful in a number of domains, including

• embedded PDF fonts, and

• fast loading Web-Fonts (you'll need additional external tools to then package as WOFF or EOT format).

class HarfBuzz::Subset Methods

new

method new( HarfBuzz::Font() :input() ) returns HarfBuzz::Subset:D;

• :$font is either a HarfBuzz::Font object or a hash of coerceable options.

• :$input is either a HarfBuzz::Subset::Input object or a hash of coerceable options.

Blob

Binary image of the subsetted font. This can be saved to a file with the same extension as the input font (typically .ttf or .otf) or embedded somehow (for example in a PDF file).

HarfBuzz subsetting currently works on TrueType, and OpenType font formats. It also accepts TrueType Collections (typically with file extension .ttc). In this case, the subsetted font id converted to TrueType format, which should be saved with file extension .ttf.

HarfBuzz::Subset::Input Methods

new

method new(
    UInt :@unicodes,      # unicode code-points to include
    UInt :@glyphs,        # glyph identifiers to include
    Str  :@drop-tables,   # additional SFnt tables to drop
    Bool :$hints=True,    # retain font hinting
    Bool :$retain-gids,   # retain glyph identifiers
    Bool :$subroutines=True,
) returns HarfBuzz::Subset::Input:D;

Creates a font subsetting profile. Only the characters specified in :@unicodes and/or the glyph identifiers specified in :@glyphs are retained.

COERCE

method COERCE( %(
    :@unicodes, :@glyphs, :@drop-tables,
    :$hints, :$retain-gids, :$subroutines,
) returns HarfBuzz::Subset::Input:D;

An object can be coerced from a Hash of options.

Installation and Dependencies

• This module requires at least Rakudo 2020.11.

• As of early 2022, HarfBuzz's 3.0.0+ font subsetting capability is not packaged yet.

• In the meantime, HarfBuzz font shaping and subsetting libraries can be downloaded and built from https://github.com/harfbuzz/harfbuzz.