Document Scanner

Put the document on a darker, plain surface such as a wooden table or a dark cloth, so its edges stand out. Hold the phone parallel to the page, fill most of the frame with it, and use daylight or a bright room without your own shadow falling on the paper. Tap the screen to focus on the text. Each photo should show one page with all four corners visible. Photos taken at a slight angle are fine; the scanner straightens them.

Each page can use its own look; pick the one that suits the document.

The photo is reduced in size and the brightest large region, the paper, is found with an automatic threshold. Its extreme points become the four corners, which you can adjust. A perspective transform, calculated from those corners, maps the slanted page onto a rectangle, and every pixel of the output is sampled from the full-resolution photo. Clean divides each pixel by the average brightness around it, which flattens shadows and turns the paper white; black and white compares each pixel with that local average, so text stays readable even where the lighting is uneven.

To make the text searchable and selectable, open the PDF in the OCR PDF tool, which recognises the text in many languages, including Hindi. Compress PDF can make a large scan smaller for e-mail or upload portals with size limits, and Merge PDF combines scans with other documents. For receipts and bills, scanning in black and white usually gives the smallest file.

Many free scanner apps upload every page to their servers to process it, keep copies in an account, or add a watermark unless you pay. Identity cards, bank statements, medical reports and signed contracts are exactly the documents you would rather not hand to a third party. Here the photos are opened, straightened and turned into a PDF by your own browser, so the pages never leave your phone or computer, and nothing is stored once you close the tab.