Document scanner
Shoot a page with your phone camera or upload a photo — the tool finds the edges, corrects the perspective, removes shadows and combines pages into one PDF. Photos are processed on your device only.
Free, no sign-up
Photos are processed on this device only and live in this tab's memory — they are gone after a reload; only the settings are saved in the browser. Photo metadata (EXIF, location) is removed during processing.
Add pages
Shoot the document with the camera or upload photos — the page edges are found automatically, the page is straightened, the text is sharpened and pages are combined into one PDF.
Drop photos here or paste from the clipboard (Ctrl+V)
How the tool works
Capture
The rear camera at high resolution: the page outline is highlighted live on the video; the shutter is a button, Space or Enter; auto-capture can fire when the outline holds still for one second. Or upload photos — several files, drag and drop or paste.
Page edges
Corners are found automatically; move them with a mouse or finger (with a 3× magnifier under the finger) or with the arrow keys. “Find edges” repeats the search, “Whole image” resets the frame.
Straightening
The page quadrilateral is mapped to a rectangle: the size comes from the edge lengths or the A4/Letter proportion, with 90° rotation either way. The result updates while you drag the corners.
Filters
Original, “Colour+”, greyscale and B&W with a before/after slider. Shadows and uneven light are removed by estimating the paper background.
Pages and PDF
Up to 40 pages: reorder by dragging or with buttons, duplicate, retake, delete. The PDF is written by our own writer right in the browser — A4, Letter or fit to image, with margins and JPEG quality; the size estimate is shown in advance. Each page can be downloaded as JPEG or PNG.
Algorithms and standards
- Page detection: greyscale (Rec. 601) → 5×5 Gaussian blur → Sobel operator with non-maximum suppression (the Canny step) → a Hough transform where each edge pixel votes only for angles near its gradient direction → pairs of opposite sides → the convex quadrilateral with the longest confirmed edges.
- Perspective: a homography from 4 point pairs (an 8×8 system, Gaussian elimination); every output pixel maps to a point on the photo with bilinear interpolation.
- Shadows: the paper background is estimated per block (maximum after blur, dilation, smoothing) and the image is divided by it — the paper becomes evenly white.
- B&W: Sauvola adaptive threshold T = m·(1 + k·(s/128 − 1)) over a local window; mean and variance via integral images.
- PDF: ISO 32000-1 (PDF 1.4 compatible), JPEG embedded without re-encoding (DCTDecode filter), a cross-reference table with exact offsets.
Original
- What it does
- Straightening only, colours as captured.
Colour+
- What it does
- The paper background is levelled (shadows removed), text darker, stamps and signatures keep their colour.
Greyscale
- What it does
- Same shadow removal, no colour — a smaller file.
B&W
- What it does
- Sauvola adaptive threshold: clean white background and black text, the smallest file.
A4 (ISO 216)
- Size
- 210 × 297 mm
- PDF page
- 595.28 × 841.89 pt
- Long / short
- 1.4143
Letter (ANSI A)
- Size
- 8.5 × 11 in (215.9 × 279.4 mm)
- PDF page
- 612 × 792 pt
- Long / short
- 1.2941
150
- A4
- 1754 px
- Letter
- 1650 px
200
- A4
- 2339 px
- Letter
- 2200 px
300
- A4
- 3508 px
- Letter
- 3300 px
Browser support
- The camera needs HTTPS and getUserMedia: Chrome, Edge, Firefox, Safari (iOS 14.3+). The torch works only where the camera reports it (usually Chrome on Android).
- Processing runs in a background thread (Web Worker) so the page stays responsive; if it is unavailable, the same code runs on the main thread.
- Photo upload: JPEG, PNG, WebP. Save iPhone HEIC photos as JPEG first (or switch the camera to “Most Compatible”).
Limitations
- No text recognition (OCR): the PDF consists of images, its text cannot be selected or searched.
- Edges are found when the page stands out from the background and all four sides are visible; a white sheet on a white desk, folded corners or fingers on the edges — adjust the corners by hand.
- Curved pages (an open book) are straightened as flat — the curve remains.
- “From the edges” proportions come from the side lengths in the photo; under strong perspective choose A4 or Letter for exact proportions.
- Photos are scaled to 4096 px on the long side; at most 40 pages per document.
Privacy
- Photos and PDFs are made on your device and are not sent to a server; camera frames never leave the browser. Only a short summary — the page count, PDF format and filter — may go with a request.
- Photo metadata (EXIF, location, phone model) is removed: every image is re-encoded through a canvas.
- Only the settings (filter, paper, PDF, quality, auto-capture) are kept in localStorage; photos live in this tab's memory only.
- The camera starts only on your click and stops with “Done”, when the tab is hidden and when you leave the page.
- Analytics receives only the fact of an export, its format and a page-count range — no content.
- The result reaches us only if you send a request yourself and keep the “Attach the result” box ticked — the form shows exactly what will be sent. Files and images are never sent with a request.
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InterLAB builds business software: document capture from the camera, archives, search and integrations with accounting systems. The first conversation about your task is free.
- The first short conversation is free — we choose the format
- NDA — yours or ours
- Pricing after a brief and an agreed scope