pdf-inspector

Fast Rust library for PDF classification and text extraction. Detects whether a PDF is text-based or scanned, extracts text with position awareness, and converts to clean Markdown — all without OCR.

Built by Firecrawl to handle text-based PDFs locally in under 200ms, skipping expensive OCR services for the ~54% of PDFs that don't need them.

Features

• Smart classification — Detect TextBased, Scanned, ImageBased, or Mixed PDFs in ~10-50ms by sampling content streams. Returns a confidence score (0.0-1.0) and per-page OCR routing.
• Text extraction — Position-aware extraction with font info, X/Y coordinates, and automatic multi-column reading order.
• Markdown conversion — Headings (H1-H4 via font size ratios), bullet/numbered/letter lists, code blocks (monospace font detection), tables (rectangle-based and heuristic), bold/italic formatting, URL linking, and page breaks.
• Table detection — Dual-mode: rectangle-based detection from PDF drawing ops, plus heuristic detection from text alignment. Handles financial tables, footnotes, and continuation tables across pages.
• CID font support — ToUnicode CMap decoding for Type0/Identity-H fonts, UTF-16BE, UTF-8, and Latin-1 encodings.
• Multi-column layout — Automatic detection of newspaper-style columns, sequential reading order, and RTL text support.
• Encoding issue detection — Automatically flags broken font encodings (garbled text, replacement characters) so callers can fall back to OCR.
• Single document load — The document is parsed once and shared between detection and extraction, avoiding redundant I/O.
• Lightweight — Pure Rust, no ML models, no external services. Single dependency on lopdf for PDF parsing.

Quick start

As a library

Add to your Cargo.toml:

[dependencies]
pdf-inspector = { git = "https://github.com/firecrawl/pdf-inspector" }

Detect and extract in one call:

use pdf_inspector::process_pdf;

let result = process_pdf("document.pdf")?;

println!("Type: {:?}", result.pdf_type);       // TextBased, Scanned, ImageBased, Mixed
println!("Confidence: {:.0}%", result.confidence * 100.0);
println!("Pages: {}", result.page_count);

if let Some(markdown) = &result.markdown {
    println!("{}", markdown);
}

Fast metadata-only detection (no text extraction or markdown generation):

use pdf_inspector::detect_pdf;

let info = detect_pdf("document.pdf")?;

match info.pdf_type {
    pdf_inspector::PdfType::TextBased => {
        // Extract locally — fast and free
    }
    _ => {
        // Route to OCR service
        // info.pages_needing_ocr tells you exactly which pages
    }
}

Customize processing with PdfOptions:

use pdf_inspector::{process_pdf_with_options, PdfOptions, ProcessMode, DetectionConfig, ScanStrategy};

// Analyze layout without generating markdown
let result = process_pdf_with_options(
    "document.pdf",
    PdfOptions::new().mode(ProcessMode::Analyze),
)?;

// Full extraction with custom detection strategy
let result = process_pdf_with_options(
    "large.pdf",
    PdfOptions::new().detection(DetectionConfig {
        strategy: ScanStrategy::Sample(5),
        ..Default::default()
    }),
)?;

// Process only specific pages
let result = process_pdf_with_options(
    "document.pdf",
    PdfOptions::new().pages([1, 3, 5]),
)?;

Process from a byte buffer (no filesystem needed):

use pdf_inspector::process_pdf_mem;

let bytes = std::fs::read("document.pdf")?;
let result = process_pdf_mem(&bytes)?;

CLI

# Convert PDF to Markdown
cargo run --bin pdf2md -- document.pdf

# JSON output (for piping)
cargo run --bin pdf2md -- document.pdf --json

# Raw markdown only (no headers)
cargo run --bin pdf2md -- document.pdf --raw

# Insert page break markers (<!-- Page N -->)
cargo run --bin pdf2md -- document.pdf --pages

# Process only specific pages
cargo run --bin pdf2md -- document.pdf --select-pages 1,3,5-10

# Detection only (no extraction)
cargo run --bin detect-pdf -- document.pdf
cargo run --bin detect-pdf -- document.pdf --json

# Detection + layout analysis (tables, columns)
cargo run --bin detect-pdf -- document.pdf --analyze
cargo run --bin detect-pdf -- document.pdf --analyze --json

Architecture

PDF bytes
  │
  ├─► detector         → PdfType (TextBased / Scanned / ImageBased / Mixed)
  │
  └─► extractor
        ├─ fonts        → font widths, encodings
        ├─ content_stream → walk PDF operators → TextItems + PdfRects
        ├─ xobjects     → Form XObject text, image placeholders
        ├─ links        → hyperlinks, AcroForm fields
        └─ layout       → column detection → line grouping → reading order
              │
              ├─► tables
              │     ├─ detect_rects      → rectangle-based tables (union-find)
              │     ├─ detect_heuristic  → alignment-based tables
              │     ├─ grid              → column/row assignment → cells
              │     └─ format            → cells → Markdown table
              │
              └─► markdown
                    ├─ analysis     → font stats, heading tiers
                    ├─ preprocess   → merge headings, drop caps
                    ├─ convert      → line loop + table/image insertion
                    ├─ classify     → captions, lists, code
                    └─ postprocess  → cleanup → final Markdown

The document is loaded once via load_document_from_path / load_document_from_mem and shared between the detection and extraction stages, so there's no redundant parsing.

Project structure

src/
  lib.rs                — Public API, PdfOptions builder, convenience functions
  types.rs              — Shared types: TextItem, TextLine, PdfRect, ItemType
  text_utils.rs         — Character/text helpers (CJK, RTL, ligatures, bold/italic)
  process_mode.rs       — ProcessMode enum (DetectOnly, Analyze, Full)
  detector.rs           — Fast PDF type detection without full document load
  glyph_names.rs        — Adobe Glyph List → Unicode mapping
  tounicode.rs          — ToUnicode CMap parsing for CID-encoded text
  extractor/            — Text extraction pipeline
  tables/               — Table detection and formatting
  markdown/             — Markdown conversion and structure detection
  bin/                  — CLI tools (pdf2md, detect_pdf)

How classification works

1. Parse the xref table and page tree (no full object load)
2. Select pages based on ScanStrategy (default: all pages with early exit)
3. Look for Tj/TJ (text operators) and Do (image operators) in content streams
4. Classify based on text operator presence across sampled pages

This detects 300+ page PDFs in milliseconds. The result includes pages_needing_ocr — a list of specific page numbers that lack text, enabling per-page OCR routing instead of all-or-nothing.

Scan strategies

Strategy	Behavior	Best for
EarlyExit (default)	Scan all pages, stop on first non-text page	Pipelines routing TextBased PDFs to fast extraction
Full	Scan all pages, no early exit	Accurate Mixed vs Scanned classification
Sample(n)	Sample n evenly distributed pages (first, last, middle)	Very large PDFs where speed matters more than precision
Pages(vec)	Only scan specific 1-indexed page numbers	When the caller knows which pages to check

API

Processing modes

Mode	What it does	Returns
ProcessMode::Full (default)	Detect + extract + convert to Markdown	Everything populated
ProcessMode::Analyze	Detect + extract + layout analysis (no Markdown)	markdown is None, layout is populated
ProcessMode::DetectOnly	Classification only (fastest)	markdown is None, layout is default

Functions

Function	Description
process_pdf(path)	Full processing with defaults
detect_pdf(path)	Fast metadata-only detection (no extraction)
process_pdf_with_options(path, options)	Process with custom PdfOptions
process_pdf_mem(bytes)	Full processing from a byte buffer
detect_pdf_mem(bytes)	Fast detection from a byte buffer
process_pdf_mem_with_options(bytes, options)	Process from bytes with custom options
extract_text(path)	Plain text extraction
extract_text_with_positions(path)	Text with X/Y coordinates and font info
to_markdown(text, options)	Convert plain text to Markdown
to_markdown_from_items(items, options)	Markdown from pre-extracted TextItems
to_markdown_from_items_with_rects(items, options, rects)	Markdown with rectangle-based table detection

Low-level detection functions are also available via the detector module (detect_pdf_type, detect_pdf_type_with_config, etc.) for callers who need PdfTypeResult instead of PdfProcessResult.

Types

Type	Description
PdfOptions	Builder for processing configuration (mode, detection, markdown, page filter)
ProcessMode	DetectOnly, Analyze, Full
PdfType	TextBased, Scanned, ImageBased, Mixed
PdfProcessResult	Full result: pdf_type, markdown, page_count, confidence, layout, has_encoding_issues, timing
PdfTypeResult	Low-level detection result: type, confidence, page count, pages needing OCR
DetectionConfig	Configuration for detection: scan strategy, thresholds
ScanStrategy	EarlyExit, Full, Sample(n), Pages(vec)
LayoutComplexity	Layout analysis: is_complex, pages_with_tables, pages_with_columns
TextItem	Text with position, font info, and page number
MarkdownOptions	Configuration for Markdown formatting (page numbers, etc.)
PdfError	Io, Parse, Encrypted, InvalidStructure, NotAPdf

Markdown output

The converter handles:

Element	How it's detected
Headings (H1-H4)	Font size tiers relative to body text, with 0.5pt clustering
Bold/italic	Font name patterns (Bold, Italic, Oblique)
Bullet lists	*, -, *, ○, ●, ◦ prefixes
Numbered lists	1., 1), (1) patterns
Letter lists	a., a), (a) patterns
Code blocks	Monospace fonts (Courier, Consolas, Monaco, Menlo, Fira Code, JetBrains Mono) and keyword detection
Tables	Rectangle-based detection from PDF drawing ops + heuristic detection from text alignment
Financial tables	Token splitting for consolidated numeric values
Captions	"Figure", "Table", "Source:" prefix detection
Sub/superscript	Font size and Y-offset relative to baseline
URLs	Converted to Markdown links
Hyphenation	Rejoins words broken across lines
Page numbers	Filtered from output
Drop caps	Large initial letters merged with following text
Dot leaders	TOC-style dots collapsed to " ... "

Debugging with RUST_LOG

Structured logging via RUST_LOG replaces the former debug binaries. Set the environment variable to control which sections emit debug output on stderr:

# Raw PDF content stream operators (replaces dump_ops)
RUST_LOG=pdf_inspector::extractor::content_stream=trace cargo run --bin pdf2md -- file.pdf > /dev/null

# Font metadata, encodings, ligatures (replaces debug_fonts / debug_ligatures)
RUST_LOG=pdf_inspector::extractor::fonts=debug cargo run --bin pdf2md -- file.pdf > /dev/null

# ToUnicode CMap parsing
RUST_LOG=pdf_inspector::tounicode=debug cargo run --bin pdf2md -- file.pdf > /dev/null

# Text items per page with x/y/width (replaces debug_spaces / debug_pages)
RUST_LOG=pdf_inspector::extractor=debug cargo run --bin pdf2md -- file.pdf > /dev/null

# Column detection and reading order (replaces debug_order)
RUST_LOG=pdf_inspector::extractor::layout=debug cargo run --bin pdf2md -- file.pdf > /dev/null

# Y-gap analysis and paragraph thresholds (replaces debug_ygaps)
RUST_LOG=pdf_inspector::markdown::analysis=debug cargo run --bin pdf2md -- file.pdf > /dev/null

# Table detection
RUST_LOG=pdf_inspector::tables=debug cargo run --bin pdf2md -- file.pdf > /dev/null

# Everything
RUST_LOG=pdf_inspector=debug cargo run --bin pdf2md -- file.pdf > /dev/null

Use case: smart PDF routing

pdf-inspector was built for pipelines that process PDFs at scale. Instead of sending every PDF through OCR:

PDF arrives
  → pdf-inspector classifies it (~20ms)
  → TextBased + high confidence?
      YES → extract locally (~150ms), done
      NO  → send to OCR service (2-10s)

This saves cost and latency for the majority of PDFs that are already text-based (reports, papers, invoices, legal docs).

License

MIT