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About this tool
Crop, straighten, clean up, and export a document photo entirely in your browser without uploading it.
The Private Document Scanner & Cleanup turns a phone photo of a page into a flat, straight, readable scan by dragging four corners onto the document and applying a perspective transform that maps that quadrilateral back to a rectangle. It solves a full 8-parameter homography — the same projective correction a desk scanner avoids by holding the page flat — then applies brightness, contrast and an optional grayscale or black-and-white pass using Rec. 709 luminance weights before exporting PNG or JPEG. It is for anyone who needs a clean copy of an ID, a receipt or a signed form without sending that page to a scanning app's servers.
Open Private Document Scanner & Cleanup on AltFTool — it loads instantly in your browser.
Press 'Upload document photo' for a PNG, JPEG, WebP or other browser-supported image up to 30 MB, or 'Use device camera' then 'Capture document'.
Drag the four crop corners onto the page edges — arrow keys nudge them, Shift takes larger steps — then choose Color, Grayscale or Black & white and set brightness, contrast and threshold.
Pick PNG or JPEG under 'File format' and press 'Download cleaned image' to save yourfile-cleaned.png locally.
The four-corner homography removes the keystone from an angled photo, so the page edges come out parallel instead of trapezoidal.
Each crop handle takes arrow keys, with Shift for larger steps, so you can place an edge exactly rather than fighting a touch drag.
Shoot the page from the browser camera and the frame goes straight into the editor without a round trip to any server.
Up to 30 MB and 80 megapixels. Very large images are downscaled to 12 megapixels for editing, and the exported scan is capped at 6 megapixels and 3000 pixels on its longest side to keep the file practical to email.
It converts each pixel to Rec. 709 luminance (0.2126 red, 0.7152 green, 0.0722 blue) and pushes it to pure white or pure black against a threshold you control, which defaults to 155 of 255. Lower the threshold if faint pencil is disappearing, raise it if a grey shadow is coming through as black.
PNG for text you plan to read or OCR later, especially in black-and-white mode where it compresses very small and stays crisp. JPEG, with a quality slider defaulting to 90%, is the better choice for colour photos of documents where file size matters more than exact edges.
No. Decoding, the perspective warp, the tone adjustments and the final encode all run on a canvas in your browser, so a passport page or a payslip never leaves the tab.