Scan Desk

A document scanner that never uploads your documents

The photos people scan are exactly the ones they shouldn't hand to a stranger's server — the passport page, the signed lease, the tax form, the medical bill. Every "free online scanner" wants an upload or an app with an account. Scan Desk does the whole job — perspective correction, cropping, contrast, multi-page PDF — right here on your device, and works with the internet off.

How to use it

• Drop in one or more photos (on a phone, the file button offers the camera). Each becomes a page.
• Drag the four corner handles onto the document's corners — Scan Desk warps that quadrilateral into a flat, rectangular page, the way a real scanner would see it.
• Pick a look: crisp B&W uses an adaptive threshold that kills shadows and yellow-paper tint for a true "scanned" page; grayscale and color keep the photo, just flattened and sharpened.
• Add more pages, reorder them by dragging the thumbnails, delete the duds, then Save PDF — one file, one page per photo.

Honest limitations

• There's no text recognition (OCR) — the PDF holds page images, not selectable text. It's a picture of your document, a very clean one.
• Auto-fit corners is a helpful guess, not magic; check the corners before saving, especially on busy backgrounds.
• Very large photos are scaled down for speed; the output is still comfortably print-sharp (up to ~2200px on the long edge).

Same shelf: Photo Cleaner strips GPS/EXIF from the originals · Form Desk fills and signs the PDF you just made · The Redactor blacks out what a page shouldn't show.

Part of K-Engine Local Tools — free, privacy-respecting utilities that run on your device. The perspective warp, adaptive threshold, and PDF writer are hand-written; view-source and you're reading them. MIT licensed, from the K-Engine workshop · download the source.