How to Straighten a Crooked Scan or Photo of a Document

You photographed a document at an angle because desks and hands are rarely square. The photo shows a trapezoid: the edges lean, the text tapers, and it does not read like a document. A scanner that detects the four corners of the page and applies a perspective correction turns that slanted photo into a flat, square page, whether you shoot it live or fix a photo you already took.

How do I straighten a crooked scan or photo?

Open the Scan PDF tool and either capture the page with the camera or import the crooked photo. The tool finds the page’s four corners and warps the image into a flat rectangle. If a corner is off, open Crop and drag it to the paper’s real corner, then rotate if needed and save as a PDF or JPG.

1. 1Open Scan PDF; capture the page or import the photo.
2. 2Let it detect the page corners.
3. 3Open Crop and drag any corner that is off.
4. 4Rotate if the page is sideways.
5. 5Save as PDF or JPG.

Straighten a photo you already took

This is the most common case: the crooked photo is already in your camera roll. You do not need to retake it.

1. 1Open the Scan PDF tool. On a phone, tap Import from photos; on a computer, tap Import photos. HEIC photos from an iPhone work too.
2. 2Pick the photo. The tool looks for the page edges in it automatically and straightens the page it finds.
3. 3Open the page on the review screen. If the page fills the result neatly, you are done.
4. 4If the result still shows some desk, or a corner of the page is cut off, tap Crop. Drag each corner handle onto the real corner of the paper; a magnifier appears beside your finger so you can place it exactly. You can also drag a whole edge at once.
5. 5Lost? Tap Auto-detect in the crop screen to let the tool find the page again.
6. 6Tap Rotate if the page is sideways, then Save PDF. Choose JPG in the save screen if you want a straightened image instead of a PDF.

Straighten while you scan

With the live camera, the work happens before you even see the result. Point the phone at the angled page and an outline follows the paper’s real edges, not the edges of the screen. It turns from amber to green when it is steady and captures. The saved page is already cropped and flattened. If no page edges were found at all, the crop screen opens straight away so you can set the corners yourself.

The warp is not just a crop. The scanner maps the four corners onto a rectangle, so text that leans away from you is rebuilt as if the page had been lying flat on a scanner bed.

When detection fails, do this

Why steady and high beats clever

Perspective correction is dramatic when the page is close and only slightly tilted, and weakest when the photo is taken from a grazing angle. At a steep angle, the far edge of the page is captured with far fewer pixels than the near edge, so after straightening the far lines look softer. No software can put back detail the camera never captured. Hold the phone roughly parallel to the page, and you get a PDF that looks like it came off a flatbed.

Already have a crooked PDF?

The scanner works on images, not on existing PDF files. If a page in a PDF is simply rotated by 90 or 180 degrees, use a rotate tool. If it is skewed or has a wide border, crop the PDF, or export the page as a JPG, run that image through the scanner and save it again.