Add image_coverage_fraction signal evaluator that computes the union
image coverage fraction from individual image XObject areas.
- Computes total image coverage as sum of image_xobject_areas
- Divides by page area (width * height) to get coverage fraction
- Clamps to [0.0, 1.0] to handle overlapping images (defensive)
- Returns Some(Vote::scanned(0.85)) if fraction > 0.85
Implementation uses sum for simplicity (overestimates coverage when
images overlap), which is acceptable for the 0.85 threshold as it's
a conservative signal. Can be revisited with Klee's algorithm for
greater accuracy if needed.
Acceptance criteria PASS:
✓ Page with one image covering 90% area → Some(Vote { 0.85, Scanned })
✓ Page with multiple small images totaling 50% → None (below threshold)
✓ Page with no images → None
✓ Coverage clamped to 1.0 on overlapping images
Also includes pre-existing infrastructure:
- tr3_op_count field in PageContext
- image_xobject_areas field in PageContext
- all_tr3_with_full_page_image function
- CharDensityRatioSignal evaluator
These were necessary dependencies for the new evaluator to function.
Refs: Plan section Phase 5.1.2, coordinator pdftract-22p
- Fix broken links from ../integrations/mcp-clients.md to ../cli/mcp.md
- Update link text from 'MCP Client Configuration Guide' to 'MCP Server Documentation'
- Ensures all cross-references work in mdBook build
- book.toml with title, authors, build directory, edit-url-template
- src/SUMMARY.md with complete TOC for all planned sections
- src/introduction.md: what pdftract does and doesn't do (Non-Goals)
- src/installation.md: cargo, pip, Homebrew, Docker; KU-12 caveat verbatim
- src/quickstart.md: five-minute walkthrough with executable commands
- 39 draft placeholder files for CLI reference, schema, profiles, SDKs, advanced topics, troubleshooting, FAQ
mdbook build completes cleanly with zero warnings (linkcheck optional).
See notes/pdftract-1g87.md for verification details.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
