Class FontSubsetter

Namespace

Egami.Fonts

Assembly

Egami.Fonts.dll

Writes fonts that hold only the glyphs a document uses, as PDF embedding and SVG export want: TrueType, OpenType CFF or bare CFF, with composite glyphs and seac accents closed over and unused CFF subroutines dropped.

public static class FontSubsetter

Inheritance

object

FontSubsetter

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Examples

// Keep only the glyphs a page uses, as a PDF writer embeds them: renumbered from 0, with the map to write the text with.
GlyphRun run = new Font(face, 12).Shape("Invoice 2026-10");
FontSubset subset = FontSubsetter.Subset(face, run.Glyphs.ToArray(), new SubsetOptions
{
    FontNamePrefix = "ABCDEF+",
    KeepCmap = false,
});
byte[] fontFile2 = subset.Data.ToArray();
ushort first = subset.GlyphMap[run.Glyphs[0]];

// The face's embedding permissions are reported, never enforced: the writer decides.
bool restricted = face.Embedding.HasFlag(FontEmbedding.Restricted);

Remarks

Glyph 0 (.notdef) is always kept. The subsetter reads Embedding but never enforces it: the caller decides whether a face may be subsetted and embedded.

Methods

Subset(Typeface, IEnumerable<ushort>, SubsetOptions?)

Writes a subset of a face.

public static FontSubset Subset(Typeface face, IEnumerable<ushort> glyphs, SubsetOptions? options = null)

Parameters

face Typeface

The face.

glyphs IEnumerable<ushort>

The glyphs to keep; duplicates are fine.

options SubsetOptions

How to write it, or null for Default.

Returns

FontSubset

The subset with its glyph map.

Examples

// Keep only the glyphs a page uses, as a PDF writer embeds them: renumbered from 0, with the map to write the text with.
GlyphRun run = new Font(face, 12).Shape("Invoice 2026-10");
FontSubset subset = FontSubsetter.Subset(face, run.Glyphs.ToArray(), new SubsetOptions
{
    FontNamePrefix = "ABCDEF+",
    KeepCmap = false,
});
byte[] fontFile2 = subset.Data.ToArray();
ushort first = subset.GlyphMap[run.Glyphs[0]];

// The face's embedding permissions are reported, never enforced: the writer decides.
bool restricted = face.Embedding.HasFlag(FontEmbedding.Restricted);

Exceptions

ArgumentOutOfRangeException

A glyph id is past the face's glyph count.

ArgumentException

The format needs outlines of the other kind, such as CFF output from a TrueType face; or LayoutClosure is set without RetainGlyphIds or with bare CFF output.

CorruptDataException

A kept glyph's data cannot be read.