RoaScan (roascan) — C++17 & ONNX Multi-Page OCR + MCP Server for AI Agents

RoaScan (roascan) is a local, CPU-first multi-page OCR and optical document restoration engine powered by a clean-room C++17 native core (roascan_core) and ONNX Runtime (PP-OCRv5 Latin / PP-OCRv4 English).

Designed as an Agent-First local OCR tool (Antigravity, Claude Code, Claude Desktop, Cursor, Windsurf, OpenHands) and document restoration library that runs on CPU without requiring GPU hardware, Tesseract, or Ghostscript.

Key Capabilities & Architectural Scope

1. Multi-Page Scanned Input (Lazy Streaming & Disk-Spooling):

   • Native ingestion of multi-page .pdf (rasterized page-by-page on demand), .tiff/.tif, .png, .jpg, and .bmp.

   • In Markdown/text mode (set_retain_images(False)), page bitmaps are discarded immediately after recognition (0 bytes retained in engine._pages).

   • In Searchable PDF mode (set_retain_images(True)), restored page images are spooled as compressed PNGs to an exclusive temporary directory (_spool_dir) and automatically cleaned up on engine.close(), keeping 0 bytes of raw uncompressed bitmaps in engine._pages RAM.

2. Dual High-Value Output:

   • Restored Searchable PDF (.pdf): Preserves physical page dimensions in PDF points (72 pt/inch, e.g. 595.28 x 841.89 pt for A4) and document-level metadata (title, author), applies C++17 Sauvola 64-bit integral background whitening, 1px anti-aliased ink preservation, coarse-to-fine deskew (0.1° precision), and orthogonal 90° / 180° / 270° orientation recovery with an invisible selectable text overlay (Ctrl+F).

   • Structured Semantic Markdown (.md): Automatic reconstruction of #/## titles via typographic font-height clustering, **Key:** Value pairs, multi-column reading order (XY-Cut), C++ morphological table grid-line removal, and GitHub-Flavored Markdown tables (|---|---|).

3. Built-in Model Context Protocol (MCP) Server: Ready-to-run stdio JSON-RPC 2.0 server (roascan --mcp or roascan-mcp) exposing 4 validated tools (roascan_to_markdown, roascan_to_searchable_pdf, roascan_process_document, roascan_inspect_pdf).

4. Spanish & Latin Diacritic Restoration: Built-in Hunspell lexicon with /G and /S affix expansion (ELECTRONICA -> ELECTRÓNICA, REPUBLICA -> REPÚBLICA, Pena -> Peña).

Related MCP server: pdf-inspector-mcp

Measured Footprint & Reproducible Performance

Platform Verification Status

• Windows x64 (win_amd64): Precompiled roascan_core.dll bundled in wheel (py3-none-win_amd64); verified end-to-end. Requires standard Microsoft Visual C++ Redistributable (MSVCP140.dll / VCRUNTIME140.dll).

• Linux & macOS (Experimental Source Build): Native compilation, functional OCR, MCP, and wheel builds pass GitHub Actions on both platforms. Desktop integration remains unverified there. sdist includes full C++17 sources and CMakeLists.txt (roascan-native/). Building a wheel from source (pip install . or python -m build --wheel) automatically invokes cmake via setup.py to compile libroascan_core.so / libroascan_core.dylib (requires cmake >= 3.16 and a C++17 compiler).

Repository Structure

├── pyproject.toml             # PEP 621 package definition
├── setup.py                   # CMake native builder & platform-tagged wheel packager
├── MANIFEST.in                # Complete source distribution (sdist) manifest
├── LICENSE                    # Full Apache-2.0 License
├── NOTICE                     # Provenance, SHA-256 hashes, and licensing notices
├── THIRD_PARTY_LICENSES.txt   # Full license texts for bundled third-party resources (MPL-1.1 / Apache-2.0)
├── SKILL.md                   # AI Agent discovery & usage specification
├── mcp_config.json            # Ready-to-use Model Context Protocol (MCP) config
├── roascan/                   # Python SDK, CLI, MCP Server, bundled DLL & ONNX models
│   ├── api.py                 # Stable high-level API & Bridge Contract (`run_ocr`, `RoaScanResult`)
│   └── desktop/               # Desktop capture, interactive region crop & native clipboard
├── roascan-native/            # C++17 Native Core (`roascan_core`) & CMake build
├── dotnet/                    # Experimental C# / .NET P/Invoke preprocessing bridge (`RoaScan.cs`)
├── examples/                  # End-to-end Python usage examples
└── tests/                     # Automated pytest suite (`test_functional_ocr.py`, `test_desktop_and_api.py`)

Installation (pip install)

# 1. Core library + CLI + MCP Server:
pip install roascan

# 2. With desktop tray companion & global shortcut extra:
pip install "roascan[desktop]"

# Verify installation, native C++ core, and ONNX models:
roascan --doctor

1. Python API (roascan.run_ocr)

Stable bridge contract supporting file paths, PIL images, or raw image bytes without network dependencies:

import roascan

# Run local OCR with automatic language correction & Markdown reconstruction
result = roascan.run_ocr("factura.png", language="es")

# Standard bridge contract attributes:
print(result.text)          # Reconstructed plain text
print(result.markdown)      # Structured Markdown with tables & headings
print(len(result.words))    # Detected words with bboxes & confidences
print(result.confidences)   # List of word confidence scores

# Copy recognized text directly to the Windows clipboard:
result.copy_to_clipboard()

# Save structured Markdown:
result.save_markdown("factura.md")

# Access as dictionary mapping:
data = result.to_dict()

2. CLI Usage (roascan)

# 1. OCR a file and copy text directly to clipboard:
roascan ocr factura.png --out factura.md --copy

# 2. Interactive desktop region capture (Tkinter overlay -> OCR -> clipboard):
roascan clip

# 3. Capture specific coordinates without interactive prompt:
roascan clip --bbox 100,100,700,500 --out recorte.md

# 4. Convert a scanned multi-page PDF into both Searchable PDF and Markdown:
roascan scan.pdf --pdf limpio.pdf --md out.md --lang es

# 5. Output unified, versioned JSON (includes ocr_elapsed_ms and total elapsed_ms):
roascan factura.pdf --json

# 6. Run environment & model health check:
roascan --doctor

3. Desktop Screen Capture & Tray Companion (roascan.desktop)

RoaScan includes an offline desktop companion (clean-room design: zero cloud, zero accounts, zero telemetry):

3.1. System Tray Companion (roascan tray / roascan-tray)

Starts a lightweight background companion in the Windows notification area with a global shortcut:

• Default Global Shortcut: Ctrl+Shift+O (triggers interactive region crop -> OCR -> copies text to clipboard).

• Tray Menu: "OCR región" (triggers capture), "Salir" (clean shutdown).

• Anti-Reentrancy Lock: Prevents overlapping captures if the shortcut is pressed repeatedly.

# Launch background system tray companion (default hotkey Ctrl+Shift+O):
roascan tray
# or
roascan-tray
# or
python -m roascan.desktop

# Custom hotkey or tray-only mode:
roascan tray --hotkey "Ctrl+Alt+O"
roascan tray --no-hotkey  # tray menu only
roascan tray --ui-lang en # English interface

Windows Hotkey Note: Global shortcuts registered via pynput run in normal user mode and do not require administrative privileges. However, when an elevated administrator window (UAC) has active focus, Windows restricts non-elevated global keyhooks. To change the shortcut permanently without CLI flags, use roascan config set hotkey "Ctrl+Alt+O" or set ROASCAN_HOTKEY="Ctrl+Alt+O".

3.2. Result Inspection & Editing Panel (P5)

When a region or clip is recognized, RoaScan automatically opens a lightweight, non-blocking result window:

• Editable Text Area: Review, edit, or format the recognized text before saving or copying.

• Copy: Places the currently edited text onto the system clipboard.

• Save: Exports the text as structured Markdown (.md) or plain text (.txt) to the configured save_dir (default: ~/Documents/RoaScan).

• Close / Escape: Dismisses the panel cleanly while keeping the background tray companion alive.

• Single Instance: Triggering another OCR updates the active panel and brings it to the front rather than stacking multiple windows.

# Open interactive result panel directly from CLI clip:
roascan clip --panel

3.3. User Preferences & Localization (P6)

RoaScan stores user preferences in standard platform directories (%LOCALAPPDATA%/roascan/config.json on Windows or ~/.config/roascan/config.json on Linux/macOS via platformdirs).

CLI Configuration Management:

# View active configuration and defaults:
roascan config show

# Get the path to config.json:
roascan config path

# Change preferences:
roascan config set hotkey "Ctrl+Shift+O"
roascan config set ui_lang "en"         # "es" or "en"
roascan config set ocr_lang "es"        # "es", "en", "latin"
roascan config set show_result_panel true
roascan config set copy_on_success true
roascan config set save_dir "D:/MisDocumentos/OCR"

Precedence Order:

CLI Flags > Environment Variables (e.g. ROASCAN_HOTKEY, ROASCAN_UI_LANG) > config.json > Default Values.

3.4. Programmatic Desktop Capture, Panel & Clipboard API

from roascan.desktop import (
    capture_region_and_ocr,
    show_result_panel,
    copy_to_clipboard,
    get_clipboard_text,
    load_config,
)

# 1. Capture screen region -> local OCR -> show result editor:
result = capture_region_and_ocr(interactive=True, copy_clipboard=True, language="es")
if result and result.text:
    show_result_panel(result.text, blocking=True)

# 2. Read or write native Windows clipboard without external dependencies:
copy_to_clipboard("Texto copiado desde RoaScan")
print("Clipboard actual:", get_clipboard_text())

4. Model Context Protocol (MCP) Server

Start the MCP server over stdio:

roascan --mcp
# or
roascan-mcp

Claude Desktop / Cursor / Antigravity mcp_config.json:

{
  "mcpServers": {
    "roascan": {
      "command": "roascan-mcp",
      "args": [],
      "env": {
        "PYTHONIOENCODING": "utf-8"
      }
    }
  }
}

3. Licensing & Third-Party Notices

• RoaScan Source Code (C++17 & Python): Licensed under the Apache License 2.0 (see LICENSE).

• Bundled Neural Models (roascan/models/*.onnx, *_dict.txt): Derived from PaddleOCR under Apache License 2.0. Exact bundled SHA-256 checksums and an example paddle2onnx export command are documented in NOTICE.

• Bundled Spanish Orthographic Dictionary (roascan/models/es_ES.dic): Unmodified plain-text dictionary from RLA-ES v2.8, distributed under the elected Mozilla Public License Version 1.1 (MPL-1.1) option (see NOTICE and THIRD_PARTY_LICENSES.txt).

• Runtime Dependency PyMuPDF (fitz): Not bundled or redistributed in RoaScan packages; installed from PyPI at runtime under AGPL-3.0 (or commercial license from Artifex Software, Inc.). See NOTICE for compliance details.