pdftract/tests/fixtures/lzw_repeated_orig.bin at 99317e90106abcde40ccabe4886980101099bdb9 - jedarden/pdftract - Forgejo

jedarden/pdftract

jedarden 1959ff2446 feat(pdftract-3uu6v): implement LZWDecode with /EarlyChange parameter

- Add LZWDecoder filter using lzw crate v0.10
- Support /EarlyChange parameter (default 1, late 0)
  - Early change (1): Adobe/TIFF variant, code size increases BEFORE
  - Late change (0): GIF variant, code size increases AFTER
- Full predictor support (TIFF predictor 2, PNG predictors 10-15)
- Bomb limit protection with partial bytes on exceed
- INV-8 maintained: partial bytes returned on decode errors
- 23 tests pass (19 unit tests + 4 proptests)
- Fixtures generated using lzw crate for verification

Acceptance criteria:
- Critical test /EarlyChange=0 byte-perfect: PASS
- LZWDecode without /DecodeParms defaults: PASS
- LZWDecode + /Predictor 12: PASS
- Truncated stream partial bytes: PASS
- Bomb limit honored: PASS
- proptest no panic: PASS
- INV-8 maintained: PASS

Refs: Plan Phase 1.5 line 1142, PDF spec 7.4.4

Co-Authored-By: Claude Code <noreply@anthropic.com>

2026-05-22 22:38:31 -04:00

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