Module subset 

TrueType Font Subsetter

Strips a TrueType font to only the glyphs actually used in the document. This dramatically reduces PDF size — a typical font is 50-200KB but a subset with ~100 glyphs is usually 5-15KB.

The subsetter rebuilds a valid TrueType file with remapped glyph IDs (contiguous starting from 0). This is important because PDF CIDFont width arrays and content stream glyph references must use the new IDs.

Approach

1. Collect all needed glyphs (used glyphs + composite glyph dependencies)
2. Remap old GIDs to new contiguous GIDs
3. Rebuild required TrueType tables (glyf, loca, hmtx, cmap, etc.)
4. Write a valid TrueType file with correct checksums and alignment

Structs

SubsetResult

Result of subsetting a font.

Functions

subset_ttf

Subset a TrueType font to only include the given glyph IDs.