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CornerTools

Document Scanner

Turn phone photos of pages into a clean, straight PDF — edges found for you, shadows removed — without uploading them.

Photograph each page, one after another

Your photos never leave your device

Drop images here or paste them, or

Your images never leave your device

Processed in this browser · JPG, PNG, WebP, GIF, BMP, AVIF or HEIC · up to 50 at a time

Filter

Paper whitened and shadows removed; colour kept.

Pages

Turns photos of paper into a scan: each page cut out of its background, straightened as if photographed from straight above, its paper whitened and its shadows taken out, and all the pages saved as one PDF. Take the photos with the camera here, page after page, or add photos you already have. Everything happens on your device; no photo is uploaded.

How to use it

Use camera opens the camera in the page: the page's edges are outlined as the camera finds them, and Take photo adds a page each time, so a whole document is photographed without leaving the tool. Photos can also be added from files (JPG, PNG, HEIC, WebP and others), up to 50 pages.

Each page's corners are found for you and can always be moved: Corners opens the photo with its four corners to drag, with a magnifier beside the corner being moved; a move that would fold the page is not allowed. Pages can be turned, moved earlier or later, retaken with the camera and deleted.

Filter: Enhanced (the default) whitens the paper and removes shadows, keeping colour; Black & white does the same and then makes the print pure black, the smallest files; Greyscale and Original keep the photo as it was, shadows included. Pages: each scan a page of A4 or Letter (by your country, at first), or Fit to scan, where each page takes the scan's own shape at 300 DPI. ID card puts the first two scans, front and back, on one A4 sheet at an ID card's printed size, 85.6 × 53.98 mm.

Searchable reads the pages' text, in the languages you choose, and lays it invisibly over each page, as Searchable PDF (OCR) does, so the PDF can be searched and its text copied. Limit file size saves the pages at the quality that keeps the PDF under the size you set. Download pages as JPG saves the finished pages as images instead.

How it works

The edges are found on a small greyscale copy of the photo: the print is filled in first, so lines of text are not taken for the page's edge, then the copy is blurred and its strongest straight edges found. Of the shapes two near-horizontal and two near-vertical edges make, the tool takes the largest whose sides the photo's edges follow along most of their length. A page that runs off the photo has those sides on the photo's edge. Where no page is found, the corners start at the photo's corners.

A page photographed at a slant is a trapezium in the photo, so its sides as they appear do not give its shape. The tool works the page's true shape out from the perspective: where both pairs of sides lean towards each other, the angles they meet at give the camera's focal length; where one pair stays parallel, as when the phone is tipped straight forward, a phone's main camera is assumed. The page is then redrawn from its corners, as tall as the photo resolves it, up to 3508 pixels on its longer side (A4 at 300 DPI).

Enhanced divides each pixel by the brightness of the paper around it, so shadows and uneven light become white paper, then stretches the result so the ink is dark and the paper white. Black & white then sets each pixel black or white against the average of its own neighbourhood, so faint print in a dim corner is kept.

Examples

An A4 page photographed at a slant

Photo
4000 × 3000 px
Corners
(1192, 564), (2808, 564), (2562, 2151), (1438, 2151)

Seen in the photo, the page is 0.863 times as wide as it is tall, as the far edge is narrower and the page foreshortened. From the corners' perspective the tool recovers 0.707, against A4's 0.707, and redraws the page at 1616 × 2287 px.

Frequently asked questions

Lay the page flat on a darker surface, so its edges stand out, and hold the phone over it with the page filling most of the picture. Even light without a hard shadow across the print reads best; Enhanced removes soft shadows, but a shadow darker than the ink hides it. Hold still for a moment before taking the photo, as a blurred photo stays blurred.
Photograph the front and then the back, check each one's corners, and choose ID card: both sides go on one A4 sheet at the card's real size, ready to print as a photocopy would be. To cover the Aadhaar number first, use Blur Image on the photos.
Enhanced and Black & white change the page on purpose: coloured paper becomes white and pale pencil can fade. Choose Original or Greyscale to keep the page as it was photographed; a very dark photo is marked, as Original often shows more of it.

See also