Subset a name-keyed CFF font without making it CID-keyed
Nobody has claimed this yet.
Assessment
- Difficulty
- 5/5
- Estimated time
- Over a week
- Newbie friendliness
- 45/100
Research direction
Start by reading the crate's CFF subsetting implementation and its tests; the issue does not name specific files or entry points. Check how SID-keyed fonts are converted to CID-keyed fonts, then assess how a name-keyed subset could retain glyph SIDs, strings, and a custom encoding. Done means an option preserves name-keyed fonts and tests verify that kept glyph codes still resolve by name.
Written by the indexing model from the issue text.
Description
subset converts SID-keyed CFF fonts to CID-keyed ones. That is right for new PDF output, but a PDF that already embeds a Type1C program for a simple font (/Subtype /Type1 with /FontFile3 /Subtype /Type1C) maps its one-byte codes to glyphs through glyph names (the font's /Encoding and /Differences, else the CFF's built-in encoding). A CID-keyed subset loses the names, so readers fall back to .notdef.
Would an option to keep a name-keyed font name-keyed (a charset with the kept glyphs' SIDs and the string INDEX, and a custom encoding for the kept codes) fit the crate's scope? It is the other half of subsetting fonts that existing PDFs embed; most CFF programs in PDFs are name-keyed Type1C. I can send a PR with tests if the shape is acceptable.
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- Dominant language
- Rust
- Stars
- 61
- Forks
- 16
- PR merge metrics
- No merged PRs in 30d
Getting set up
This project ships no dev container, Dockerfile or contributing guide, so setting up is up to you: start from its README, and see our first-contribution guide for the general steps.
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
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