39ca6a3552
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
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| .. | ||
| benches | ||
| bin | ||
| build | ||
| examples | ||
| proptest-regressions/parser/lexer | ||
| scripts | ||
| src | ||
| tests | ||
| __test__.pdf | ||
| build.rs | ||
| Cargo.toml | ||
| pdftract-core.cdx.json | ||
| README.md | ||
pdftract-core
The core Rust library for PDF text extraction. This crate provides the parsing, layout analysis, font encoding recovery, and text extraction primitives used by the CLI (pdftract-cli) and Python bindings (pdftract-py).
Cargo.lock Policy
This workspace checks in Cargo.lock at the repository root. This is unconventional for library crates—the Cargo Book historically suggested that only binary crates should check in lockfiles, allowing library consumers to resolve their own dependency versions.
pdftract departs from this convention for release reproducibility:
-
SLSA Level 3 provenance requires that every milestone tag produces byte-identical artifacts across builds. Without a checked-in lockfile, two runs of
cargo buildon the same commit can resolve different transitive dependency versions, producing different binary hashes. -
Multi-output artifacts—this workspace produces Rust crates (
pdftract-core,pdftract-cli), Python wheels (pdftract-py), and Docker images. All must be built from the same dependency tree. -
Supply-chain security—the lockfile pins checksums for all transitive dependencies, enabling
cargo auditto detect yanked or compromised crates. -
Downstream consumers can still ignore the lockfile if needed. Cargo allows
cargo build --frozenwith a local lockfile override, or consumers can vendor the crate with their own dependency resolution.
The tradeoff—occasional merge conflicts when PRs update overlapping dependencies—is worth the guarantee of reproducible releases. See CONTRIBUTING.md for the lockfile-update workflow.
Modules
parser: PDF spec parsing (xref, trailer, object streams, indirect references)font: Font encoding recovery, glyph name lookup, fingerprintinglayout: Page layout analysis, region segmentation, reading orderextract: Text extraction with provenance (bounding boxes, confidence scores)ocr: Tesseract integration for raster pages
Usage
use pdftract_core::{extract_text, ExtractOptions};
let options = ExtractOptions::default();
let result = extract_text("document.pdf", &options)?;
println!("{}", result.text);