~/tools/Prepare Images for Fax
2026·09·08
toolDocumentsfree

Prepare Images for Fax

Flatten, sharpen, and lay a photo of a document onto clean paper.

Türkçe: Faks için Görüntü Hazırlama

Drop images here, or

Photos of documents work — the tool flattens and sharpens them for fax.

Runs entirely in your browser. Nothing you paste is uploaded, logged, or stored.

How to use it

  1. Add photos or scans of the pages you need to fax.
  2. Keep auto-crop on so the document edges are found and the background trimmed.
  3. Pick grayscale for mixed content or black & white for pure text, and tune contrast.
  4. Build the fax-ready PDF and download it.

Why a phone photo faxes badly

Fax is a one-bit medium: every pixel is either black or white. A phone photo arrives with uneven lighting, a grey cast, shadows, and a background of whatever your desk looks like. Sent as-is it comes out muddy or half-black, because the gateway has to guess where to put the threshold.

What this tool does about it

  1. Finds the document's content bounds and crops away the surrounding desk.
  2. Places the crop onto a clean white Letter or A4 page at 150 dpi with a margin.
  3. Converts to grayscale or applies a hard black/white threshold you control.
  4. Boosts contrast so faint pencil and thin type survive the transmission.

Grayscale or black and white?

Use black and white for pure text and line drawings — it produces the crispest, smallest fax. Use grayscale when the page contains photographs or shaded diagrams that would turn into blobs under a hard threshold.

FAQ

Are my images uploaded to a server?
No. Every tool here decodes and re-encodes your file using your browser's own Canvas APIs. The image never leaves your device, which is also why it works offline once the page is loaded.
Why 150 dpi?
Standard fax resolution is roughly 204 × 196 dpi, and fine mode is not much higher. Rendering pages at 150 dpi keeps well within useful detail while keeping the PDF small enough to transmit quickly.
The result is too dark or too light. What should I change?
Adjust the black & white threshold first — it decides which grey values become black. Then use contrast to separate the ink from the paper, and brightness to correct an overall cast from poor lighting.
Can this send the fax too?
No. It produces a fax-ready PDF; you still need a fax service or machine to transmit it. Preparing the file properly is the part that determines whether it arrives legible.

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