Dewarping is the process of digitally correcting the perspective distortion that happens whenever a camera photographs a flat page from an angle instead of straight-on.
Why every phone photo of a page looks skewed
Unless the camera is perfectly parallel to the page, the far edge appears smaller than the near edge — a trapezoid instead of a rectangle. This is unavoidable geometry, not a camera flaw.
How dewarping fixes it
The app detects the four corners of the document, then applies a perspective transform that stretches the trapezoid back into a true rectangle — the same math used to "unwarp" any photographed flat surface.
Why it matters for readability
A dewarped scan has straight margins and evenly sized text edge to edge, which is what makes a phone scan readable as a document rather than looking like a photo of a document.
Does dewarping work on curved or folded pages?
Basic dewarping assumes a flat page and corrects flat perspective distortion — a page with a visible curve or fold (like a thick book spine) needs additional curve-correction, which is a separate, harder problem some scanner apps handle only partially.