How to flatten a tilted document photo
- Open a photo of a page, receipt, whiteboard, screen or painting taken at an angle.
- Four corner handles appear; if the picture has a clear page against a darker or lighter background, they are placed on its corners for you.
- Drag each handle onto a corner. A magnifier shows the exact spot while you drag; arrow keys nudge a selected corner.
- Choose the result’s shape — from the corners, A4, US Letter or an ID card — and a look: colour, greyscale or scan.
- Press Flatten and crop, then download the JPG, PNG or PDF.
When a rectangle is the wrong tool
A page photographed on a desk is a trapezoid: the far edge is shorter than the near one and the sides lean in. Rotating and cropping with a rectangle cannot fix that — some of the page is cut off and some of the desk is left in. A perspective crop uses four independent corners instead, and maps the shape they enclose onto a true rectangle with a homography, the same projective correction scanning apps use. Each output pixel is sampled from the original with a bicubic filter, which keeps fine print and handwriting crisp.
The output size comes from the average lengths of the four edges, so the page keeps its natural proportions, or from a paper shape you choose — A4, US Letter or an 85.6 × 54 mm ID card — when you know what the object is. Very large photos are processed at up to 40 megapixels.
Documents stay on your device
Receipts, IDs and contracts are exactly the photos that should not be uploaded to a stranger’s server. Here the corner search, the flattening and the PDF are all done by code running in your browser tab; nothing is sent. To straighten an ordinary photo instead, crop photo has a fine straighten control.
Frequently asked questions
What does a perspective crop do?
It takes the four corners of something photographed at an angle and maps that area onto a flat rectangle — as if the photo had been taken straight on.
How are the corners found?
By plain measurement, not AI: the picture is split into light and dark at an automatic threshold, the largest clear region is taken as the page, and its four outer corners are proposed. You always check them.
Is the result lossless?
No — flattening resamples every pixel. A bicubic filter keeps text sharp, and the result says it was resampled. For a lossless cut, use lossless crop.
What does the scan look do?
It turns greyish, unevenly lit paper white and darkens the ink while keeping its colour, so a phone photo reads like a scan.
Can I save it as a PDF?
Yes — pick PDF under Save as. A4 and Letter shapes go on a page of that size. For several pictures in one PDF, see crop image to PDF.