When this tool is useful
Flattening a photographed document, sign, card, poster, or rectangular surface after its four visible corners have been identified deliberately.
How local processing works
The browser validates corner order, convexity, area, edge lengths, and output limits, computes a projective mapping, samples source pixels for the rectangular destination, and encodes a flattened PNG.
How to use it
- Prepare and preserve the source: Keep an unchanged source, choose one supported static image, and start with conservative settings. Flattening a photographed document, sign, card, poster, or rectangular surface after its four visible corners have been identified deliberately.
- Run the bounded local operation: Process the decoded pixels in this browser; stop and adjust instead of accepting an ambiguous result. The browser validates corner order, convexity, area, edge lengths, and output limits, computes a projective mapping, samples source pixels for the rectangular destination, and encodes a flattened PNG.
- Inspect the flattened result: Check all four corners and straight edges against the source, inspect text and circles for distortion at 100%, confirm the output aspect ratio, and retain the uncropped photograph until the corrected copy is accepted.
Important limitations
The tool cannot recover hidden, blurred, overexposed, curved, folded, or out-of-frame detail. Incorrect or nearly collinear corners are rejected, and strong perspective correction can stretch noise or reduce sharpness; it does not detect corners automatically.
Verify the downloaded result
Check all four corners and straight edges against the source, inspect text and circles for distortion at 100%, confirm the output aspect ratio, and retain the uncropped photograph until the corrected copy is accepted.
Private by design
Your files stay in this browser. The tool does not upload the source or output to our servers.
Questions and answers
When is this tool useful?
Flattening a photographed document, sign, card, poster, or rectangular surface after its four visible corners have been identified deliberately.
What does the local operation do?
The browser validates corner order, convexity, area, edge lengths, and output limits, computes a projective mapping, samples source pixels for the rectangular destination, and encodes a flattened PNG.
Which limitations matter?
The tool cannot recover hidden, blurred, overexposed, curved, folded, or out-of-frame detail. Incorrect or nearly collinear corners are rejected, and strong perspective correction can stretch noise or reduce sharpness; it does not detect corners automatically.
How should I verify the result?
Check all four corners and straight edges against the source, inspect text and circles for distortion at 100%, confirm the output aspect ratio, and retain the uncropped photograph until the corrected copy is accepted.