61b94b49d2
Implement Phase 5.3.2a: histogram-based contrast normalization for OCR preprocessing. The algorithm stretches the input gray value range (from 1st to 99th percentile) to the full [0, 255] output range, improving downstream binarization effectiveness. Key implementation details: - 256-bin histogram computation for percentile calculation - 1st/99th percentile robustness against hot pixels and artifacts - In-place mutation for performance (no double allocation) - Proper error handling for uniform images and invalid dimensions - Overflow-safe arithmetic using i32 intermediate values Acceptance criteria: - Image with [50, 200] range → stretched to [0, 255] - Hot pixel robustness: single 0/255 pixels handled correctly - Uniform image → early return with UniformImage error - Invalid dimensions (zero width/height) → InvalidDimensions error - Full performance: < 50 ms for 8 MP images Closes: pdftract-6dki1 |
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| .. | ||
| benches | ||
| build | ||
| examples | ||
| proptest-regressions/parser/lexer | ||
| 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);