Contrast Stretching Utility for Scans: Rescue Faded Scans, Free & Online

Use this free contrast stretching utility for scans in your browser. No sign-up, no download and no upload: everything runs on your own device, so your data stays private.

What this tool does

Old scans often use only a narrow band of grey, which makes them look washed out even though the information is there. Contrast stretching remaps your chosen input range to the full black-to-white range, so faint detail gains separation. This tool does that on a canvas from your local scan or a demo gradient, and reports the before and after ranges so the change is measurable, not just visual.

How to use it

Paste or type your local scan and low-high levels in the box above.
Adjust any settings, such as cutoffs, scales or styles, to match your data.
Click the run button and read the output below the tool.
Check the summary numbers before you copy anything into a document.
Copy the output, code or image into your figure, slide or report.

Worked example

Use the demo gradient with low 10 and high 240. The dark-to-mid gradient stretches to full black-to-white, and the report shows the input range widening to the full output range. Tighten the range to 60–180 and mid-tones gain even more separation, at the cost of clipping the extremes.

Tips for better results

Stretch a copy, never the only original, and record the levels you used.

Honest limits

Stretching cannot recover detail that was never scanned, and aggressive settings clip highlights and shadows to pure white and black. Keep the original scan untouched.

Choosing the right settings

Start with the default values. They are chosen to show a sensible result at once, so you can see the layout before you touch your own data. Then change one setting at a time. Changing one thing at a time is the fastest way to learn what each control does, and it stops two changes from cancelling each other out. If the output looks wrong, check the input format first: a missing comma, a swapped column or a stray space causes most errors, and the tool reports what it received in its summary line.

Using the result in a figure

For a figure, keep the output simple. One message per figure, short labels, and a caption that states the method and the settings you used will serve readers better than a dense, decorated chart. If a journal or supervisor will see the result, note the tool name, the input values and any cutoff in your methods or caption, so the figure can be reproduced later. That habit also helps you: six months from now, the caption is the only record of how the figure was made.

Common questions

Do I need an account? No. The contrast stretching utility for scans runs entirely in your browser with no sign-up and no saved data.

Is my data uploaded anywhere? No. Your local scan and low-high levels stays on your device, which is why the tool is safe for unpublished work.

Can I use the output in a paper or presentation? Yes. The output is yours to reuse; just check it visually once, note the settings in your caption, and credit the method, not the tool, in your references.

What if the result looks wrong? Check the input format first, then change one setting at a time. Most errors come from a missing comma, a swapped column, or a value outside the expected range, and the summary line under the tool shows what it actually received.

Try the contrast stretching utility for scans above with the sample data, then with your own. It is free, it needs no account, and it works in any modern browser.

When you reuse the result, keep a short record of the inputs and settings you used. A one-line note in your project file, such as the data pasted, the cutoff chosen and the date, is enough to reproduce the figure later. If a collaborator questions a number, that note lets you rebuild the exact output in seconds instead of guessing what changed.

Embed this tool on your website — free

Copy the code below to add this working tool to your own page. A small credit link stays with it — that’s all we ask.