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LibPDF: Implement subr_number biasing for CFF font programs

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Nico Weber 2023-10-18 09:27:27 -04:00 • committed by Tim Flynn
parent 4dc4de052a
commit 185573c03f
1 changed files with 15 additions and 0 deletions
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15
Userland/Libraries/LibPDF/Fonts/Type1FontProgram.cpp
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@ -373,6 +373,21 @@ PDFErrorOr<Type1FontProgram::Glyph> Type1FontProgram::parse_glyph(ReadonlyBytes
case CallSubr: {
auto subr_number = pop();
if (is_type2) {
// Type 2 spec:
// "The numbering of subroutines is encoded more compactly by using the negative half of the number space, which effectively
// doubles the number of compactly encodable subroutine numbers. The bias applied depends on the number of subrs (gsubrs).
// If the number of subrs (gsubrs) is less than 1240, the bias is 107. Otherwise if it is less than 33900, it is 1131; otherwise
// it is 32768. This bias is added to the encoded subr (gsubr) number to find the appropriate entry in the subr (gsubr) array."
if (subroutines.size() < 1240)
subr_number += 107;
else if (subroutines.size() < 33900)
subr_number += 1131;
else
subr_number += 32768;
}
if (static_cast<size_t>(subr_number) >= subroutines.size())
return error("Subroutine index out of range");