extracting-with-ocr

Imported from xberg-io/xberg (plugin/skills/extracting-with-ocr/SKILL.md). Install upstream with npx skills add xberg-io/xberg --skill extracting-with-ocr. Copyright stays with the author.

Extracting with OCR

Use this when a document is image-based: scanned PDFs, photographed pages, screenshots, JPEG/PNG/TIFF with text. Xberg auto-OCRs raster images and auto-detects PDFs that lack a text layer. Force it on when extraction returned empty/garbled text from a PDF that "looks" textual.

When to force OCR

• Extraction returned an empty content field, but the file opens visually.
• The PDF text layer is junk (copy-paste from a viewer produces gibberish).
• You want consistent output across mixed scanned + digital PDFs.

xberg extract scan.pdf --force-ocr=true
xberg extract scan.pdf --ocr=true --ocr-language eng

If a page has an unreliable text layer, --force-ocr=true re-rasterizes and runs OCR on every page.

Backends

Tesseract is the default and ships with the CLI — no extra install. Other backends are opt-in:

Pick Tesseract first. Switch only when accuracy is unacceptable.

Language packs

Tesseract uses ISO 639-2 codes. Default is eng. Combine with +:

xberg extract menu.jpg --ocr=true --ocr-language "eng+deu"
xberg extract bilingual.pdf --ocr-language "eng+jpn"
xberg extract any.pdf --ocr-language all   # all installed packs

Install missing packs at the OS level:

# macOS
brew install tesseract-lang

# Debian/Ubuntu
sudo apt install tesseract-ocr-deu tesseract-ocr-jpn tesseract-ocr-fra

# Specific lang only
sudo apt install tesseract-ocr-<iso639-2>

Xberg fails fast with a helpful error if you request a language pack that is not installed. Read the error — it names the missing file.

Useful flags

• --ocr=true — enable OCR (auto-enabled for images and scanned PDFs).
• --force-ocr=true — OCR every page even if a text layer exists.
• --disable-ocr=true — never OCR (extract embedded text only or fail).
• --ocr-language <lang> — single code or +-joined list, or all.
• --ocr-backend <tesseract|paddle-ocr|vlm|candle-trocr|candle-paddleocr-vl|candle-glm-ocr|candle-deepseek-ocr> — pick backend.
• --ocr-auto-rotate=true — pre-rotate via the auto-rotate model.
• --acceleration <cpu|coreml|cuda|tensorrt|auto> — ONNX accelerator for paddle-ocr / auto-rotate / layout models.

Performance tips

• Cache is on by default. Repeated extraction of the same file + config is instant. Do not pass --no-cache=true unless you have a reason.
• For batch OCR, use xberg batch *.pdf --ocr=true — internal worker pool parallelizes across CPU cores. Cap with --max-concurrent N if memory is tight.
• Raise --target-dpi (default 300) only for low-resolution scans. Higher DPI is slower; 200 is usually enough for printed text.
• Enable --ocr-auto-rotate=true only when pages may be rotated; the classifier adds latency.
• On Apple Silicon, --acceleration coreml typically beats CPU for paddle-ocr and layout detection.

Config file alternative

Long flag chains belong in xberg.toml — auto-discovered from cwd upward.

force_ocr = true
output_format = "markdown"

[ocr]
backend = "tesseract"
language = "eng+deu"
auto_rotate = true

Then just run:

xberg extract document.pdf

Common failure modes

• "missing tessdata" — install the language pack at OS level (see above).
• Empty content on a scanned PDF without --force-ocr — the file has a bogus zero-width text layer. Re-run with --force-ocr=true.
• OCR on a rotated page — add --ocr-auto-rotate=true or pre-rotate.
• Garbled CJK output — ensure the right language pack is installed and passed via --ocr-language; consider paddle-ocr for Chinese/Japanese.

See references/cli-reference.md and references/configuration.md in the sibling xberg skill for the full flag and config schema.