THotPDF.SubsetLoadedFonts Method
Rewrites supported embedded TrueType, OpenType CFF, raw CFF, and Type 1 programs so they retain only glyphs reachable from loaded-document content
Declaration
function SubsetLoadedFonts(
const Options: THPDFLoadedFontSubsetOptions;
out AInfo: THPDFLoadedFontSubsetInfo): Integer; overload;
function SubsetLoadedFonts(
out AInfo: THPDFLoadedFontSubsetInfo): Integer; overload;Reachability
Page content is always scanned, including text-showing operators and resource-local font selections
IncludeFormXObjects recursively includes invoked Form XObjects with inherited resources, cycle detection and a bounded nesting depth
IncludeAnnotationAppearances includes normal, rollover and down appearances as well as state dictionaries, and also follows Form XObjects used by those appearances when enabled
Every character code follows its declared encoding, then any Type0 CMap and CIDToGIDMap, before reaching the stable embedded glyph ID; existing CID maps and ToUnicode data are not renumbered
TrueType composite glyphs retain their recursive component closure, while COLR v0 layers and COLR v1 glyph paint dependencies retain every referenced outline
Type 1 simple fonts follow Standard, WinAnsi, MacRoman, or MacExpert encoding plus Differences, then rewrite unused CharStrings in PFB, PDF split binary, or hex PFA data without changing the embedded stream layout
Options
| Field | Default | Meaning |
|---|---|---|
MinimumSavingsBytes | 1 | Minimum encoded stream reduction required before a candidate is adopted |
EnforceSignaturePermissions | True | Refuse every rewrite when the document contains a signature field |
IncludeFormXObjects | True | Trace invoked nested Form XObjects |
IncludeAnnotationAppearances | True | Trace annotation appearance streams and states |
Result and safety
The return value is the number of embedded font programs rewritten, while AInfo reports scan coverage, mapping or decoding failures, used glyphs, byte savings and signature consequences
A font program is left byte-for-byte unchanged when any reachable code cannot be mapped, its format is unsupported, subsetting fails, or the encoded candidate misses the savings threshold
Type 1 rewriting fails closed for multiple binary PFB segments, an unparseable explicit simple-font encoding, a missing requested glyph name, or an unsupported CharString layout; unknown COLR versions and sfnt programs without sparse outline tables also remain unchanged
All candidates are analyzed before mutation, and the default signature policy returns zero with RefusedBySignaturePolicy set; disabling the policy permits rewriting and sets SignaturesInvalidated whenever a signed document changes
Example
var
Info: THPDFLoadedFontSubsetInfo;
begin
PDF.LoadFromFile('input.pdf');
if PDF.SubsetLoadedFonts(Info) > 0 then
PDF.SaveToFile('subset.pdf');
end;