Working with CFF Fonts

Working with CFF Fonts

This guide shows how to load and inspect CFF font internals — charsets, encoding tables, dictionaries, and index structures — using Aspose.Font FOSS for Python.

Compact Font Format (CFF) fonts store glyph outlines as Type 2 charstring programs. Aspose.Font FOSS for Python provides dedicated classes in the aspose_font.cff namespace for reading CFF charsets, encoding tables, dictionaries, and indexes.

CFF Charset

CffCharset maps glyph IDs to PostScript glyph names. Call CffCharset.standard() to obtain the built-in ISO Adobe charset, then use name_for() and gid_for() to translate between glyph IDs and names.

from aspose_font.cff.charset import CffCharset

charset = CffCharset.standard()
name = charset.name_for(1)   # PostScript name for GID 1
gid  = charset.gid_for("A")  # GID for PostScript name "A"

CFF Encoding

CffEncoding maps character codes to glyph IDs. The standard encoding covers the Adobe Latin character set; use unicode_to_gid() to look up individual code points and get_all_codepoints() to list every mapped value.

from aspose_font.cff.encoding import CffEncoding

enc = CffEncoding.standard()
gid = enc.unicode_to_gid(0x41)
codepoints = enc.get_all_codepoints()

CFF Dictionary Parsing

CffDict.from_bytes() parses a raw CFF DICT blob into an operator-keyed mapping. Each operator key maps to a list of numeric values that configure the font, such as default width or subroutine offsets.

from aspose_font.cff.dict_ import CffDict

d = CffDict.from_bytes(raw_bytes)
vals = d.get(21)   # retrieve values for operator 21

CFF Index

CffIndex.from_reader() parses a CFF INDEX data structure from a binary stream. INDEX structures are arrays of variable-length data used for name tables, string tables, and charstring storage within CFF fonts.

from aspose_font.cff.index import CffIndex
from aspose_font._io import BinaryReader  # internal API — may change between releases
import io

reader = BinaryReader(io.BytesIO(raw_index_bytes))
index = CffIndex.from_reader(reader)
print(f"INDEX entries: {len(index)}")

Type 2 Charstring Interpretation

Type2Interpreter.interpret() executes a Type 2 charstring and returns a GlyphPath.

from aspose_font.cff.type2 import Type2Interpreter

interpreter = Type2Interpreter()
glyph_path = interpreter.interpret(charstring_bytes, private_dict)

Tips and Best Practices

• Use CffEncoding.standard() as a baseline; override with from_reader() for embedded encodings
• CffDict.to_bytes() lets you re-serialise modified dictionaries
• Charstring interpretation is needed only for raw glyph outline extraction; GlyphAccessor covers most use cases at a higher level

API Reference Summary

See Also

• Aspose.Font — Enterprise Documentation
• Aspose.Font for Python — Enterprise Documentation