Scan to PDF
Scan to PDF: photograph pages with your phone camera, choose a filter, create the PDF. The photos are processed in your browser and never uploaded.
Source: pdf-lib – Andrew Dillon (MIT). Updated: .
How it is calculated
In short: You photograph a document, the tool turns it into a clean scan page and puts all pages into one PDF. It works on phone and computer, with no app, no account and no upload.
How it works
- On a phone tap “Choose images” and pick “Take photo”; on a computer drag in photos or paste them with Ctrl + V.
- Set the order with the arrows. Choose page size (A4, Letter or image size), orientation and margin.
- Choose a scan filter. “Document” is best for most pages.
- Click “Save scan as PDF” and download.
What the filters do
- Document: turns the image gray, estimates the brightness of the paper and divides it out. Shadows and brightness gradients disappear and the paper becomes white.
- Black and white: pure black and white. This gives very small files and suits text, not photos.
- Color: removes shadows but keeps the colors, for example for stamps or colored print.
- Original: no processing, the photo goes into the PDF unchanged.
Honest limits
- The tool does not straighten crooked photos or cut out the background. Shoot from above in even light if you can.
- The filter is a calculation, not a text recognizer (OCR): the PDF contains images, not searchable text.
- Very large photos are reduced to about 2,400 pixels on the long side, which gives roughly 200 dpi on A4.
Privacy
The photos are processed only in your browser and are not uploaded.
Frequently asked questions
How can I scan a document with my phone and save it as a PDF?
Tap “Choose images” here, pick “Take photo”, photograph all pages and tap “Save scan as PDF”.
Can I put several pages into one PDF?
Yes. Add all photos, put them in order with the arrows and save one PDF.
Why does my scan look gray or blotchy?
Usually because of shadows or uneven light. The “Document” filter removes them; also try to shoot in even light.
Is the PDF searchable?
No. It contains the pages as images. Text recognition (OCR) is not included.
Are my photos uploaded?
No. Everything runs in your browser and the photos never leave your device.
Sources and legal basis
- pdf-lib – Andrew Dillon (MIT)
- Wikipedia – Thresholding (image processing): adaptive thresholding by local mean
- Bradley, D., Roth, G. (2007): Adaptive Thresholding Using the Integral Image. Journal of Graphics Tools 12(2)
- MDN – <input type="file"> accept: take a photo with the camera on mobile devices
- ITU-T T.81 / ISO/IEC 10918-1 – JPEG
- W3C – Portable Network Graphics (PNG) Specification
- Google for Developers – An image format for the Web (WebP)
- AOMedia – AV1 Image File Format (AVIF)
- MDN – Image file type and format guide
- MDN – HTMLCanvasElement.toBlob()
- Open-source licenses of the libraries used (MIT, LGPL-3.0)
As of:
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